Today I stumbled on this with FMPA 15 on Mac OS X 10.11.5.
In a form view all text field were extremely slow to edit (typing was as slow as 1 character per second), Filemaker process CPU usage skyrocketed.
This in on a form view, with stored text field.
Committing the record, changing layout and going back to it didn't change anything. As it was reproducible in that session, I took the time to sample the process for 60 seconds. At first before entering the field, and then editing it slowly.
After that sample, I did a system diagnose.
Quitting filemaker solved the issue, but it may re-happen, something is wrong, I never stumbled on this in prior release.
Files are in TSGal Mailbox