Delete the problematic Tab and create it from the scratch. You should also post this as an Issue report in forums.filemaker.com.
This might be one approach but I chose to instead revert back a day to a clean master of the file, before I did any work on the Tab and portal and started from there.
So far no crashes...
We make backups of our files ever 20 or 30 minutes ( when developing offline ) and keep a development log of what we did for TS and for cases like this. eg what layouts, scripts VL, etc were touched.