Bosch WAK28261GB/16 motor circuit error E21

The story starts a couple of weeks ago….

Over night one of our sockets RCDs tripped with the washing machine mid-cycle, I reset it and the machine appeared ready to carry on from where it left off except that it was convinced that the door was open when it was shut and locked. I tried turning it off and on again in various ways (control dial, mains) to no avail so used the manual release to open the door. The door was then unlocked but the machine behaved as though the door was open when it was closed, all the controls appeared to work normally but it would not start a cycle, just beeped as though the door was open. After a bit of research here and on other forums I checked all the connections to the door interlock, all were fine but the interlock seemed rather worn so bought a new one and replaced it. Made no difference.

Next we called out an engineer who said it was probably the main PCB and not worth replacing and should get a new machine.
As the machine is only 5 years old I was very reluctant to do this so took the circuit board out and found it had 2 obvious areas of damage. I sent it off to QER (as suggested in here, I think) and they promptly sent it back, fixed but advised the damage was likely caused by an external fault. Replaced the PCB and the machine no longer thinks the door is open (hurrah!) and seemed happy to start a cycle. I tried the spin/drain cycle, the drain pump happily pumped away but the drum did not move. After a minute or so the cycle time skipped from 12 to 10 then straight to 2 minutes, without the drum motor starting at all. It then sat clicking (from the timer/control board area) for several minutes before I turned it off. It then showed an error E21. More research found this is a motor circuit fault and given age of machine worth checking the brushes. I did this and they were certainly worn, one right down to the copper wire, the other almost as worn. Ordered new brushes, thinking this was bound to be the external fault that caused all the problems, replaced them (without removing the motor) but still no joy: Error E21, have reset the error but the motor still does not move on any washing cycle or when I tried to put the machine through a test cycle.
So, removed the motor, checked that I had properly replaced the brushes (good contact etc) and had a look at the motor, it does have quite a lot of carbon from the brushes dusting all over the inside but no obvious damage. I removed the little motor PCB and carefully looked at that, which appears fine. Replaced everything and made sure all contacts well connected etc but still no joy. Shows E21.

My question is really, what to do now? My husband would have bought a new machine the first day it stopped working, without any further investigation, so the level of “I told you so” and general smugness is getting unbearable. I feel it is terrible to be throwing away a machine that is only 5 years old so would much rather fix it but cannot justify spending much more unless I can pretty much guarantee it will work. I don’t have a multimeter but could probably borrow one, is it worth checking the connections to the motor? If so, any guidance as to how? Is it possible that there is another fault on the PCB that might have been overlooked given the two very obvious areas of damage that were fixed? The fact that the motor does not respond at all (totally silent) makes me suspicious the fault is electrical rather than mechanical but I am guessing!

I would be very grateful for any help/guidance, if that is, give up and get a new machine so be it.

Thanks in advance.