@Trail A1 series? If you remove the nozzle there is a graphite (?) plate that has screws on the backside that can come loose and cause issues with bed probing. You need to remove the plate to get at them.
I’m sure Bambu has instructions for this but I don’t know what terminology they use.
But another possible cause is that the nozzle isn’t actually seated correctly. It is possible to install them so that the latch closes but the nozzle can still move around.
@polakkenak @SorteKanin While you *can* "upgrade" the MK4S to a Core One, it's more like a complete rebuild with very little parts carryover. It takes a lot of time and doesn't really make any financial sense.
The MK4S is competent at being what it is, which is an un-enclosed bed slinger. It inherently isn't going to be as fast as the Core One, it will struggle more with materials that want a stable printing environment, and it's less suited for printing tall things.
For the time being it uses the same technology the Core One does, though it almost certainly will not support INDX ever. If you really want to do multi-material/color stuff, the MK4S probably isn't the right choice.
As far as the open source stuff, IMO it's only a step backwards if one wants to be an absolutist about such things. I'm not here to say whether that is right or wrong, but in practical terms I don't think there's much of a difference with the new licensing, if one is not trying to sell knock-off printers.