Cannot add new record to custom entity after run any workflow action

I have custom secondary entities linked to case and have tabs to show the list and with New button to add the record. The issue is, every time after I click any case workflow action, I come to click new button to create the custom secondary record and cannot save it. It will show validation error message what ever come from the case workflow action an error message or blank message if the workflow action does not have error string, and sometime show invalid date time value. It is very strange, even I click Opportunity workflow action also causing this Case related issue and the error message would from opportunity workflow action. It looks the CRM remember something to make this validation invalid like locked it. After I run + - New Case and then save or cancel, it will be working again. Logout/login can release the lock as well.

Anybody have idea? Thanks in advance.