Getting error message when user is trying to submit the assignment  in all environments

Error:You have lost the ability to make this change because a change elsewhere has taken precedence over the change you made here. Please click on the assignment below to continue.

Note:Default locking and Lock will be released after 15 minutes as per the current configuration.

Any inputs are much appreciated!

***Edited by Moderator Kayla to update Content Type from Discussion to Question***