diff --git a/src/AasxCsharpLibrary/AdminShellPackageEnv.cs b/src/AasxCsharpLibrary/AdminShellPackageEnv.cs
index dfe265e9b..bf0a81efb 100644
--- a/src/AasxCsharpLibrary/AdminShellPackageEnv.cs
+++ b/src/AasxCsharpLibrary/AdminShellPackageEnv.cs
@@ -21,7 +21,6 @@ This source code may use other Open Source software components (see LICENSE.txt)
 using System.Threading.Tasks;
 using System.Xml;
 using System.Xml.Serialization;
-using static AasCore.Aas3_0.Reporting;
 
 namespace AdminShellNS
 {
@@ -385,7 +384,12 @@ private static (AasCore.Aas3_0.Environment, Package) LoadPackageAasx(string fn,
                 foreach (var x in xs)
                     if (x.SourceUri.ToString() == "/")
                     {
-                        originPart = package.GetPart(x.TargetUri);
+                        //originPart = package.GetPart(x.TargetUri);
+                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                        if (package.PartExists(absoluteURI))
+                        {
+                            originPart = package.GetPart(absoluteURI);
+                        }
                         break;
                     }
 
@@ -397,7 +401,12 @@ private static (AasCore.Aas3_0.Environment, Package) LoadPackageAasx(string fn,
                 xs = originPart.GetRelationshipsByType("http://www.admin-shell.io/aasx/relationships/aas-spec");
                 foreach (var x in xs)
                 {
-                    specPart = package.GetPart(x.TargetUri);
+                    //specPart = package.GetPart(x.TargetUri);
+                    var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                    if (package.PartExists(absoluteURI))
+                    {
+                        specPart = package.GetPart(absoluteURI);
+                    }
                     break;
                 }
 
@@ -748,7 +757,12 @@ public bool SaveAs(string fn, bool writeFreshly = false, SerializationFormat pre
                     foreach (var x in xs)
                         if (x.SourceUri.ToString() == "/")
                         {
-                            originPart = package.GetPart(x.TargetUri);
+                            //originPart = package.GetPart(x.TargetUri);
+                            var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                            if (package.PartExists(absoluteURI))
+                            {
+                                originPart = package.GetPart(absoluteURI);
+                            }
                             break;
                         }
                     if (originPart == null)
@@ -774,7 +788,12 @@ public bool SaveAs(string fn, bool writeFreshly = false, SerializationFormat pre
                     foreach (var x in xs)
                     {
                         specRel = x;
-                        specPart = package.GetPart(x.TargetUri);
+                        //specPart = package.GetPart(x.TargetUri);
+                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                        if (package.PartExists(absoluteURI))
+                        {
+                            specPart = package.GetPart(absoluteURI);
+                        }
                         break;
                     }
 
@@ -921,7 +940,12 @@ public bool SaveAs(string fn, bool writeFreshly = false, SerializationFormat pre
                                 foreach (var x in xs)
                                     if (x.TargetUri == psfAdd.Uri)
                                     {
-                                        filePart = package.GetPart(x.TargetUri);
+                                        //filePart = package.GetPart(x.TargetUri);
+                                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                                        if (package.PartExists(absoluteURI))
+                                        {
+                                            filePart = package.GetPart(absoluteURI);
+                                        }
                                         break;
                                     }
                             }
@@ -933,7 +957,12 @@ public bool SaveAs(string fn, bool writeFreshly = false, SerializationFormat pre
                                 foreach (var x in xs)
                                     if (x.SourceUri.ToString() == "/" && x.TargetUri == psfAdd.Uri)
                                     {
-                                        filePart = package.GetPart(x.TargetUri);
+                                        //filePart = package.GetPart(x.TargetUri);
+                                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                                        if (package.PartExists(absoluteURI))
+                                        {
+                                            filePart = package.GetPart(absoluteURI);
+                                        }
                                         break;
                                     }
                             }
@@ -1299,10 +1328,19 @@ public long GetStreamSizeFromPackage(string uriString)
             {
                 if (_openPackage == null)
                     return 0;
-                var part = _openPackage.GetPart(new Uri(uriString, UriKind.RelativeOrAbsolute));
-                using (var s = part.GetStream(FileMode.Open))
+
+                PackagePart part = null;
+                var uri = new Uri(uriString, UriKind.RelativeOrAbsolute);
+                if (_openPackage.PartExists(uri))
                 {
-                    res = s.Length;
+                    part = _openPackage.GetPart(uri);
+                }
+                if (part != null)
+                {
+                    using (var s = part.GetStream(FileMode.Open))
+                    {
+                        res = s.Length;
+                    }
                 }
             }
             catch (Exception ex)
@@ -1329,7 +1367,12 @@ public Stream GetLocalThumbnailStream(ref Uri thumbUri)
             foreach (var x in xs)
                 if (x.SourceUri.ToString() == "/")
                 {
-                    thumbPart = _openPackage.GetPart(x.TargetUri);
+                    //thumbPart = _openPackage.GetPart(x.TargetUri);
+                    var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                    if (_openPackage.PartExists(absoluteURI))
+                    {
+                        thumbPart = _openPackage.GetPart(absoluteURI);
+                    }
                     thumbUri = x.TargetUri;
                     break;
                 }
@@ -1393,7 +1436,12 @@ public ListOfAasSupplementaryFile GetListOfSupplementaryFiles()
                 foreach (var x in xs)
                     if (x.SourceUri.ToString() == "/")
                     {
-                        originPart = _openPackage.GetPart(x.TargetUri);
+                        //originPart = _openPackage.GetPart(x.TargetUri);
+                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                        if (_openPackage.PartExists(absoluteURI))
+                        {
+                            originPart = _openPackage.GetPart(absoluteURI);
+                        }
                         break;
                     }
 
@@ -1404,7 +1452,12 @@ public ListOfAasSupplementaryFile GetListOfSupplementaryFiles()
                     xs = originPart.GetRelationshipsByType("http://www.admin-shell.io/aasx/relationships/aas-spec");
                     foreach (var x in xs)
                     {
-                        specPart = _openPackage.GetPart(x.TargetUri);
+                        //specPart = _openPackage.GetPart(x.TargetUri);
+                        var absoluteURI = PackUriHelper.ResolvePartUri(x.SourceUri, x.TargetUri);
+                        if (_openPackage.PartExists(absoluteURI))
+                        {
+                            specPart = _openPackage.GetPart(absoluteURI);
+                        }
                         break;
                     }