Fatal Error when copying slide from one session to another

[rvl]

Using Captivate 2019 update #5.

I'm getting a fatal error when copying a slide from one session to another.  This is a last ditch effort trying to solve another problem/bug where the Properties panel has disappeared and the suggested fixes have not worked.  I have wasted an hour on this problem so far.  Anyway, suggestions for fixes are appreciated.

[Lilybiri]

Sure you are on 11.5.5? I don't give the rest of the full number becauseit depends on the OS.

I am on Windows on that new version. I just double-checked and had no problem to copy/paste slides from one project to another project with the same resolution; If the projects have different themes the usual button appears under the slide where you can choose between Source and Destination theme.

Try cleaning the Preferences?