OK. The wiki advises to check the buffers screws to make sure they’re not overtigthened. The way I understand the wiki is that they may protube and hit the bed. I don’t know how this could be possible but worth checking as you installed it recently.
Step 7: Check AMS hub/ Filament buffer’s screws
If you have installed the AMS-HUB or AMS-BUFFER, if the screw is over tightened, that may also stick the z-axis when the bed is near the nozzle, so try loose these two screws for 1~2 rounds :
