Email id is getting truncated even after correction

Hello community members,

Has anyone come across issue where emailid gets truncated even after correction?

There are few users in our system who have very long name , as a result there userid(which consist) of email is getting truncated , 

both email id and userid have length of 151 already on sys_user table, so increasing length might not be the solution.

We do not see import records for 'sys_user' table for those records (long names).

Hence, we are confused which particular integration or script is reverting back the changes , the only thing we can see in audit history is updated by "system".

Can anybody assist here?