When using BTT, any time on any application I try to Shift/Option/CMD/etc. + Click, this pops up and interupts the intended actions. For example, CMD + Click on Chrome does not open a link in a new tab, rather BTT just hijacks the click and nothing occurs. I cannot find these Null actions anywhere.
could you post s screenshot of your the „normal mouse“ section in BTT? (BTT shows these menus if a trigger like cmd+left click has been defined multiple times in BTT)
you must have added them previously as BTT doesn’t come with a default setup.
For the sync - you probably had multiple presets on different machines, after the initial sync you need to decide which preset to keep enabled and disable the not needed ones.