Semi Auto Tool Change problem

[pierrerdurand]

Using grblhal setting #341: Tool Change Mode: Manual Touch Off @ G59.3.
I ran a test following Stephan's youtube tutorial.
The iosender setting Agressive Buffering was OFF. (When it is on another problem arises. Described later)
After the firt section of the .nc program completes the spindle move to the G59.3 position.
Tool change is made and a $TPW command is issued. The TLO red square does not appear (as in Stephan's tutorial)
The spindle moves back to its last position at the work area and stops. No further movement is made.
I Have tried this over and over without success. Any help would be appreciated.

Am running on a Teensy board V2.07 with prebuilt iosender XL v2.0.37.
Have recorded the screen and video at this link if any have interest:

https://www.screencast.com/t/wa0CGji08

Two files of settings are attached.
GRBLHal Console.pdf
GRBLHal Settings Tools Change.pdf

When I check the Agressive Buffering ON, the spindle starts to spin after reaching the G59.3 position for the tool change, with no way to stop it.

pierre