I left a print going overnight and took off the result in the morning. Left the printer on. Then tried to do another print and the nozzle gouged the bed on the left side.
Turn the printer off, lift both z towers as high as they’ll go, print again and it’s fine, don’t even need to re-level.
I guess at some point overnight after it had finished the steppers were disengaged, and the toolhead caused the left z tower to drop.
So I guess this is an advice post - turn machine off and reposition both z towers after it has been idle for a while, otherwise your levelling is ruined cause the controller doesn’t know the left axis has moved.
This makes me quite sad. I hope SM have considered new splitter modules which can drive each axis individually, then the controller can at least attempt to do something about this.