Sets the UI module into a mode when the printer is in charge of processing the buttons (from all sources).
That means the MMU will detect its buttons but it will not react upon them.
This mode is important for error recovery when the printer needs to do some stuff before the MMU (like preheating the nozzle).
If the MMU receives a command LoadFilament with a slot number SL we reject
the command to avoid moving the selector (effectively cutting the piece of filament present in FINDA).
That includes the scenario when the selector is standing at the very same slot SL, because the filament could be held by the printer (i.e. loaded in the nozzle).
There is one special case though - same slot AND filament load state == InSelector (it MUST NOT be anywhere farther)
D.R.racer
VintagePC