FileMaker Pro 15 Advanced version 126.96.36.199 running on Mac OS X 10.12 Sierra.
Frequent notices about uncaught inconsistency, option to crash and lose unsaved changes or continue. If opt to Continue get same message next time I try to may a change. SO only real option is Crash. Then get the option to send report to Apple, which I have done.
I have also going to saving changes in layouts and scripts frequently in case this happens.
I went to FMPA 15.0.2 as soon as it was available and then to Mac OS X 10.12 Sierra when it was available.
This problem did not occur on Mac OS X 10.11 El Capitan