After 1500+ hours on my Bambu X1C combo I started having issues with filament feeding within the AMS unit. The PTFE tubes are consumable items and should be checked and replaced when needed. I probably should of replaced mine much earlier and will now check them more often.
Here is what very worn tubes look like. These we almost worn through on the under side you can t see easily where the filament gets dragged back into the roll. I have seen some people post pictures of filament puncturing the tubes and going all over the inside of the AMS unit.
Bambulabs sells pre-cut replacement PTFE tubes for the AMS at reasonable price on their website. The kit contains eight tubes at two different lengths. This is two sets of replacements. The shorter tubes are the for center and the longer for the outer locations. Directions on opening the AMS and replacing the PTFE tubes can be found here on their website. Its a very simple task and wont take you much time at all.
So why do these PTFE tubes wear? The constant dragging of the filament is what causes the wear and where the pressure points are is what will wear through sooner. I had significant wear closer to the AMS feeder as there is a hard turn there. Using filaments such as carbon, glow in the dark, sparkle and other more abrasive filaments can cause more wear. But over time any filament is going to end up wearing out these PTFE tubes especially with how often the AMS retracts filaments for switching or purging them.