One of the nice things about these mounts is that they don't have a lot of moving parts and are easy to work on and keep in adjustment.
The simplest explanation for your click would have been the large pulley scraping on the nearby plastic post that receives the housing's screw. Easy to fix in that case, but unfortunately it sounds like that's not it. Perhaps an unhappy worm block bearing or a ding in the worm itself? Best you can do is just keep going and investigate...
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras: Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer: Thinkpad x230, Win7Pro/64