Sorry to all experiencing issues with GuiMods on recent v3.50 betas. I am aware of the issue and need to update my mods to the generator logic. Unfortunately, I my time is occupied with a home move and have no time to work on the significant changes needed. (SetupHelper continues to function even under the latest betas.)
I just checked and GuiMods is compatible with v3.42.
You should not need to reinstall anything when switching firmware. My packages will reinstall automatically after the update unless you manually uninstall them via SetupHelper or the command line.