UM2+ buildplate level problems after Pronterface intervention.

[nzo 16]

My UM2+ has been working amazingly well for print after print. One of those prints is a printhead-mounted dial gauge. I've used this gauge with Pronterface via USB as a possibly easier way to level the buildplate. The UM2+ does not seem to allow a constant variation in z-axis position which is why I used pronterface.

I didn't realise Pronterface behaves differently with UM2+, i.e. in Pronterface the z-axis UP controls work in reverse - the buildplate tries to move down and resulted in a brief chattering grinding sound (belts?) and the DOWN controls caused the buildplate to move up very slowly (about 1/4 the speed of the UM2+ normal speed. I abandoned Pronterface and went back to stand-alone UM2+ to level the buildplate.

What was unexpected was that now, after the pre-heat and pre-extrusion phases, the buildplate only rose to about 20mm below where it was expected. Consequently the print started 'in the air'. Several attempts resulted in the same height shortfall.

I did a Cura and UM2+ reset but no change. Does the UM2+ retain its old Pronterface settings in a cache for a while?

Thanks for your input!