I created a simple test to isolate the problem with clkMux.v using ForMux_config.json. I then tried to run the openlane flow for user_project_wrapper.v with config.json that generated the LVS errors. Any help or ideas would be greatly appreciated!

@Christian Duffee using small macros can cause problems. If the macros are smaller than the power rail pitch, they may not get connected to power. You have to be careful with placement. Try looking at the power grid and see where the macros need to be moved to intersect with the power rails.

@Mitch Bailey okay thanks I'll try that