This is a pretty weird one but you guys have had an answer for everything so far.

I take the train to work so I leave my 997 in the parking lot. When I get back to my car the lumbar support will sometimes be maxed out. Seems to happen mostly on hot days.

Weird thing is when I get into it in the morning it's fine after being in the garage for longer than in the parking lot. Only difference I can think of is I don't lock it while it's in the garage? (might be red herring).

I'm even open to just pulling a fuse to leave it where it is, I don't really have a need to manipulate the lumbar.

Really stumped on this one, if anyone has any clues it would be greatly appreciated!

I randomly have the same issue, but it has been infrequent enough that when it happens I just adjust it back to a position of my liking.

The lumbar support is an airbladder. The interior of the car, being hot, as you noted, would cause the air in the bladder to expand and give you the perception that its maxed out. When it cools over night the air in the bladder would contract and it would feel "normal" again.

It may be filling when you unlock the car. As a test you could detach the negative battery cable, wait a few minutes, reconnect, and save the seat / mirrors to memory.

if you have memory seats, it might just be the seats being eccentric. I have had my car for almost 10 years, and the seats definitely make some "decisions" on how it responds to key input.

Try unlocking the car with your other key if you have a seat memory profile saved to you main key. Can rule out a few things if no difference....

LOL - being eccentric

I also occasionally experience many quirky, eccentric, inconsistent electrical behaviours

A programmer I used too work used the term 'unlucky numbers'

I had that issue, I think I figured out it had to do with the bladder sensors? They're kinda janky, basically a string through the middle of the bladder that pulls on the position sensor as the bladders expand. There's always some play in the string that seems to mess things up.

I think I fixed it by just setting the bladders empty and saving that to memory, I didn't find I really needed them to be comfortable. Anyway if you want to inspect the way they work it's not very hard to pop out the center of the seatback cushion and see what's going on.