Drains and then the aquastop is actuated allowing inlet water but only for about 1 sec. Then machine drains out again but the heat exchanger drainage valve remains energised.
I disconnected the lead to the aquastop, started the cycle again and measured mains volts across the aquastop for a good few seconds. Swapped the flow sensor but problem persists.
Can be that it’s not happy with the drain pump speed or the heat pump speed.
Have you tried opening the door 3 or 4 times within the first 90 seconds to try and cheat it past the self test stage?