Ah, it's a typical problem. The PTFE wears out. You should have a tight fit when you try to remove/install it. If it's loose, you got to flip the side and use the unwear one, or just buy the PTFE. The rostock max V2 use this type of device and wears out from time to time.

When it wears out, filament will leak between the PTFE/extruder, and will jam/leak everywhere ruining your prints.