I have made a minimal patcher that show how Max crashes when we try to change the container name on several mubu object, and how it depends on a specific ordering.
mubu_crash.maxpat (7.5 KB)
As a workaround, I am simply making sure that Imubu receives the name change prior to mubu.play, but this is for sure a bug.
I am using Win 10, Max 8 64 bits, Mubu 1.9.13 (I think so, but I cannot remember where to check version)
Here is the crash dmp file, in case it is useful
Max-2020-06-21_20-20-52-1f74e2b.dmp (1.4 MB)