My AMS is having problem with loading and retraction of late, after some diagnoses and quick fix, I discover the cause maybe related to the curvature near the end of a spool. Each time when error message pops, it always occurs when a spool is running out. (Its running out not already run out) As filament loads, the strain is wrapped on smaller and smaller circle, the last several turns of firmament is tightly bent at the tip of discontinuity, this creates resistance when moving through the feeding loop. It can stuck or break when forced against loop connectors especially at the extruder assembly when its curvature misaligns with the gear. I think this problem is not unique to the AMS, all material switch mechanism has to deal with at some point. Fixing is easy, if fail to load you just try insert it multiple times, usually 2 or 3 attempts will have the extruder catch it, do it immediately after AMS pulls out. If stuck, just disconnect the tube from extruder and pull out the remains. 9 out 10 times you will not need to disassemble the hall sensor. Even if you do, I recommend try switch to manual filament load, it will purge. The error message is attribute to the AMS but it’s not the AMS’s fault in these cases, the first thing you should check is what happed at the extruder end.
Welcome to the forum.
There are various fixes for the issues the AMS has. You can print a top for the feeder which holds a length of PTFE which will help smooth the transition into the feeder as the filament runs low. You can also print a spool weight holder for the centre which will help assist the rollers turning. And you can print a piece that goes underneath the AMS which helps align the PTFE into the filament hub.
There’s also various fixes to make the entrance where the PTFE enters the extruder smoother.
The PTFE tube and feeder button doesn’t always work either. On long withdrawals, having too long of a tube will cause the feed button to engage and release the filament causing an error. It thinks the filament broke off in the AMS. It’s happened to me several times. All my buttons have about 16mm showing above the button. I thought about making them longer but that would just add more torque to the release button. The original reason for the PTFE tube was to reduce wear on the AMS feed entry point. I would try to make them shorter but I’m too lazy to change out 16 of them. 