One-turn map R symplectic deviation: 0.152312E-11 warning

[zhuruihu]

I am designing a ring with interaction region. I first finished the optics of the interaction region and then the other parts of the ring. But when I combine the optics of the interaction region and other parts together, One-turn map R symplectic deviation: 0.152312E-11 warning ocurrs. I wonder why this happens.
ring:line=(matching1,7fodo1,matching2,12(fodo_arc1,fodo_arc2,fodo_arc3),matching3,matching4,20fodo2,matching5,12(fodo_arc4,fodo_arc5,fodo_arc6),matching6,matching7,8*fodo3,matching8,real_all);
use,sequence=ring;
twiss;
real_all is the interaction region, others are other parts. The interaction region and other parts can run smoothly with Twiss command.