I forgot until looking at your photo that the mini uses a Bowden tube, not direct drive like the MK3S+. Did you replace/switch the nozzle around the time this all started happening? With Bowden tubes, there are a few problems that can arise that you don’t see on direct drive. The end of the Bowden tube (that is inside the extruder/hote end assembly) can get deformed or clogged. If you can check that, you may find an issue. Other than that, when swapping nozzles I always had to put the nozzle in part of the way, then push the Bowden in further, then tighten the nozzle.