Don`t normally get involved with Miele but had no choice with this one.
Inlet/Outlet light flashes.
Machine fills and empties ok but when put on programme it fills to level then stops,circulation pump(i assume ) operates for a few seconds then inlet/outlet starts flashing and machine goes off.
Have checked pump and valve but everything seems ok.
Have you checked the sump and filters?
Had a similar one where they had been washing jam jars to recycle and the labels had become detached and gone into a pulp clogging the filter area.
seems like machine is not sensing output pressure form circ pump. Make sure circ pump impeller is clear also had pressure switch blocked/faulty ( mounted on pump ).
clayside
Clayside might just have hit nail on head about machine not sensing pressure from circulation but from experience its more likely to be a fill time out.
Check inlet hose filter, inlet hose for kinks, remove top & left hand side panel & check water is coming into fill chamber, some of these 646’s have a flowmeter on inlet hose.
Most of them monitor water level over a short period of time & if correct level isn’t achieved fault is shown.
Circulation pump is easilly removed if needed, check impellors for obstruction.