Epic Games Launcher Crashing each time it is run.

After worse than usless support from Epic Games,I’m hoping this forum maybe able to help. Everytime I run Epic Games Launcher, it starts loading, gives me the usual “new game” pop-up messages then crashes with error message in debug dialogue of “Assertion failed: IsValid() [File:d:\build++portal+release-live+compile\sync\engine\source\runtime\core\public\Templates/SharedPointer.h] [Line: 851]”.

Uninstalled and re-installed, ran as admin.
Window 10 - sufficent spec to easily run the launcher. Up-to-date
Previously has worked fine but had the error for a couple of months
Any advice appreciated
Thanks in advance