Adding a new case record throws a new error in client side js.

Hello everyone!
I have been running into an issue for quite some time now that has to do with the case object. Whenever i create a new case by clicking into the save button at the mini page for cases, i get the following error in client side JS. I have not overridden the save handler method in the case mini page source code and even though the error happens the record is saved successfully. Has anyone else run into this issue? If so could you please help me out, thank you very much!