10 Feb, 8am (UK) its only happened a few times in the last 24hrs, so getting less frequent. I mostly just ignore it now, clearing the change password message without even attempting to insert the password. I reverted back from 2FA, purely because when I was trying to insert a password, it was easier to use one I knew, rather than go through the process of generating one; also, 2FA made no difference to the problem.
One thing I am trying to keep an eye on; I have a couple of Hotmail addresses, the one that ends in .co.uk is the one that seems to cause the problems; the one ending .com I don't think has had the same issue.
I'm giving it another week and if its still happening, I think I will start migrating over to google email. The Outlook app works fine on my devices, but it doesn't suit my needs, Hub+ does.