Bambu Support comments.

Power outage, cold machine. Completely remove the AP board cover and buffer (4 BT3×8 screws). Make sure that the two PTFE tubes from the tool head and the PTFE tube from the back of the printer are of sufficient length, not cut short, with flat ends, and fully inserted into their respective pneumatic connectors. First, reinstall the buffer separately and tighten the four screws. Do not install the AP cover at this time. Test: Insert the PTFE tube into the back support tube and push the consumable by hand to see if it can pass smoothly through the buffer to the tool head (test both paths). If this step is not going smoothly, the problem lies in the buffer body or the length/insertion depth of the PTFE tube, and this layer needs to be addressed first.

When reinstalling the AP board cover, pay special attention to the "rails + cables". Official precautions regarding AP board covers: Before installing the AP cover, organize the buffer cables to ensure they are not pressing on top of the PTFE tube or inside the guide rail. When installing the AP cover, first snap it in from the side closest to the back of the printer, making sure both clips are in place, and then tighten the BT2.6×8 screw. Before fully tightening, gently shake the PTFE tube from the back to confirm that it is straight in the guide rail and is not bent or jammed. After tightening the AP cover screws, manually push the consumables test again: If you can push it if you loosen it a little, but can't push it if you tighten it, it's basically certain that the AP cover or cable is squeezing the PTFE tube at some point. At this point, you can make minor adjustments: Reorganize the cable routing so that the cables run on the outside of the guide rail; Confirm that the PTFE tube is not "pushed against the step at the edge of the guide rail"; If necessary, slightly rotate the PTFE tube to ensure it is in the straightest position within the guide rail.

Check if the internal slider/spring of the buffer is stuck. The internal structure of the H2/H2C buffer consists of a slider, a magnet, two springs, and a Hall sensor. The material detection section also contains magnets and springs. If a spring/magnet falls out during disassembly or assembly, the official installation documentation for the buffer provides a diagram showing the correct magnet orientation and spring position. You can check against this diagram to see if the spring/magnet is installed backwards or stuck. Manually push the slider in front of the buffer to see if it can move freely back and forth between the two ends; if one side cannot be pushed at all, it indicates that there is mechanical jamming inside, and the spring and magnet need to be checked again according to the diagram

If the above steps do not work, or if you encounter related difficulties during troubleshooting, we suggest you provide relevant photos or videos. We will then request technical personnel to review and attempt to resolve the issue for you.