Hello, we´re having this issue randomly 3, 4 times a week.
Suddenly de web clients see a message saying " take note and contact administrator" or something like that.
We looked the log and says
C:\Program Files\FileMaker\FileMaker Server\Web Publishing\publishing-engine\cwpc\fmscwpc.exe
"Web Publishing Engine process has terminated abnormally."
Restarting both servers solves the problem.