Keyboard on 2018 MacBook Pro goes rogue

What: OK- brand-new (bought in September, receive in October after all manner of problems with damage which resulted in a replacement machine having to be sent) and rather expensive top of the range MacBook Pro which-

Problem History: -has already been completely and UTTERLY reformatted (not restored- I was made to completely start over) due to problems with-

1. random shut downs,
2. the beachball appearing after years of me not seeing it on ANY of my dozen or so other Mac,
3. the occasional "jumping out of the page" cursors, and-
4. Mail misbehaving to the point that I had to completely rebuild my 15 email address inboxes from scratch twice so as not to risk bringing the problem in, in case it was a problem in my other Mac's Mail programme.

Add to that ^ that one of its four Thunderbolt ports was running slower with the one device plugged into it when compared to that same device plugged into one of the other ones... It was this last issue which resulted in a Genius Bar appointment.

Current Problem: Fast forward through a month of That Warm Place Down Below and over eight hours (no exaggeration) of phone calls, chats, screen-shares and the aforementioned Genius Bar appointment, and I have a keyboard which started out adding an additional space randomly while typing in Mail, Chrome, Pages and Text Edit.

I was advised to do the various resets (which I thought might also address the weird shut downs etc) but no change. Well- maybe a little.

Then it started to delete more than one email on a single click, and also not deleting lines of text when the delete key is held down. In other words- doing the exact opposite of what I am trying to do- single fast click to delete one item or single held click to delete lines of text.

In case it is relevant- I had noticed that, right after the reformat, the Keyboard was set to off in regard to Key repeat. I have tried all variants of on and off, slow and fast- still no better.

Important to note that I have two other MacBook Pros which I use without problem, so it isn't me being butter-fingered or new to the machine or its settings. I know that I will need to take it in again, but I am just trying to help myself here as the appointments are few and far between at an Apple Store well over an hour from me (in the UK).

Anyone know of this, and what it might be? I understand that this, the 2018 four Thunderbolt with Touchbar, is not covered under the Keyboard Repair Scheme so have to assume that what I am experiencing is not the same. 😟