+1The piston will keep spinning when all the way in so you are OK on that.
Can’t tell you what the click was?? I don’t remember any click when doing mine.
Only thing I can suggest (and you seem to have already done this) is to just redo that caliper, and be sure the slides are good and lubed and is sliding good.
The click might be the "one way clutch" in the caliper housing... but yeah, the piston keeps spinning even after it's retracted all the way. Once the piston is flush with the rubber dust boot, it's completely retracted.