The key just continued to take longer and longer to remove. Up to 7-8 minutes occasionally.
Today I pulled everything apart down to the gear shift blind. I've replaced that before so went back in to see if anything was amiss.
Dusty and dirty in there but the blind was intact. A good clean up and some rubber grease under the blind, reinstall and test.
It worked first go. It worked again when everything was all back together and a third time after a short drive.
Interestingly, when I reconnected the negative to test it, I also gave the pos cable a tweak. It was 3/4 of a turn loose. That was a new battery installed as the previous one was less healthy than it should've been.
So now I'm wondering if it was the poor battery in the first place, and a loose connector on the replacement. All else has been ok.