Had/have exactly the same issue. Went through a very similar series of troubleshooting, including a similar post on this forum. Came up with two key bits of useful information.
1. You absolutely must balance your mount perfectly. Chances are this will solve most/all your issues. If you have an unbalanced mount then the gear will either be working too hard to hold the unbalanced weight back, or needing extra torque to drag that weight up. If you're balanced then there will still be load put on the gears at points...I've noticed a change in the tone during slewing when the load increases as the weight (and thus centre of gravity) moves around...but it shouldn't be so much that everything crunches up together. Here's an example of the problem I was having - https://www.youtube.com/watch?v=kPROlB3gjSc - but I realised during troubleshooting that I had a counterweight on the mount but nothing at the other end to balance it out. So the moment the counterweight bar went beyond about the 5 o clock mark the worm gears didn't have enough torque to pull the weight up and the teeth meshed together.
2. If you're still having chugging/grinding/crunching noises when slewing and then the wheel flips back and forth when tracking then you probably need to adjust the worm gear. This video will tell you all you need to know - https://www.youtube.com/watch?v=mLXE_BMKVAw&t (worth watching the whole thing but it's the bit from 3:48 - 5:26 that you mainly want to watch). If you do this then be careful. First time I did it I made the worm gear too tight and the whole thing seized up. Then I adjusted it and made everything too loose, so there was a loads of movement in the gears. It really is about moving the gears and wheels by fractions of mm.
I pretty much have my mount working smoothly now. Still the occasional issue when slewing from one point in the sky to a completely different point but that can normally be resolved with a spot of manual tracking and re-syncing.
Mount: iexos-100 with PMC-8
Scopes: Startravel 102
Camera: Nikon D7500
Software: Deep Sky Stacker, Siril, Photoshop