Xray test plan can not be edited when Test PLan has more than 100 tests

Hi Team,

One of my user is facing strange problem while updating the test plan.

When he clicks on edit button, and tries to update a date there, he gets this error when click on update button:

Issue for key RAVEN_IGNORE does not exist or is not a Test nor a Test Set."

What can be the reason for it?

I attached screenshot,