Hi all, 

My coworker and I have been experience this bug for a while now.

What happens is sometimes when creating drawings for our assemblies, the assemblies disappear from our model view. The assembly is not set to "hidden". Also, the assembly in the model tree cannot be expanded to show its parts or etc. It usually set itself to lightweight.

The following screenshot illustrates the assembly in the model tree that cannot be expanded for example:

Rebuilding does nothing. Usually if I suppress and unsupress the assembly it fixes the issue, but the bug will reoccur shortly after in the same session.

Does anyone have a fix to prevent this ?

I'm using SolidWorks 2018 SP4.0

Thanks!