Buz_Light - Just to say I am not ignoring your message. Had a very busy day at work and now reading through all the messages and watching the videos and replies with interest (haven’t finished yet, and need to go out for a few hours so will probably only continue tomorrow).
I already saw that your issue is beyond my understanding. This is a case where I would call DavecUK and @MediumRoastSteam to the rescue, and I see both are already on your case - so you are in the best hands.
The only contribution I can make at this stage DavecUK and @MediumRoastSteam is re your comments about the pump starting “on it’s own” in the first video (published on the other forum). To me it looks like Buz_Light is manually pressing the button behind the lever with his finger, is he not?
Anyway, I need to rush out now so will read the rest when I get a chance.