During the development of a class occasionally we may receive this error message

wrong argument types in variable assignment

The error only occurs when during runtime.  I believe the issue is that the server has one copy of the class whereas your client has a different copy.  you can resolve the issue by clicking on the class and doing a full compile of the class.  If the class has a parent class (extends ___) then occasionally it is necessary to select the  parent class, right-click, and choose Add-ins > Compile forward.