So have agreed on a deal to a 2019 Autobiography and the driver & passenger seat both have a pronounced bulge sticking out up at the shoulder height of the seat. Dealer said this would be sorted, however wondering has anyone else come across it before, and if it was an awkward fix?
Have come across it previously when looking at an AB previously, but didn’t pay too much attention as ended up not going for that car anyway.

Click image to enlarge

I have a 2014 AB with the massage seats, if I had to guess, I'd say that they have failed in this position.
Try them and see if they are operable.
Not sure how to reset them.

The massage function still works to be fair, just those feckn lumps sticking out at the top!

If you have the many, many, many way seats in that one, push the headrest up/down button fore and aft - there is a shoulder support section of the seat that may be the culprit in your case - feels funny and makes you hunch over if someone has mal-adjusted it....
W. 2017 - L405 SC - WOW! just WOW!
2014 - L405 4.4
2010 - L322 3.6 - Carried me 100,581 miles then broke big-time

There are 10 types of people in this world;
Those that understand binary,
and those that don't.

Ended up needing new units inside the seats! The shining light of buying from a main dealer and extended warranty!

Do you have details of what units they replaced, I have similar problem on my MY19 AB and the massage function does not fully operate on either seat - OBD Codes show massage module back carrier.