Hahaha ... 200 mile highway journey last night, on a regular route of mine, and the car didn't miss a single lane change, neither my deliberate empty-road experimental ones nor normal in-traffic driving. One of the lane changes took maybe 5 seconds, but all the rest were sub 3-second. No recent software updates, So bang goes my theory ...
I'll make some more, considered, experiments at different times of the day.
Most of the lane change failures I've seen with AP1 (2.52.22) is when the lane I want to move to is a new lane created by a merging road/on-ramp.
My guess is that the car sees the right-most lane (here in the US) as the breakdown lane (solid line). Then when it becomes a newly created lane, the car still interprets it as a break-down lane until a certain amount of distance/time has passed and the lane markings (dashed lines) may be more obvious. Just my WAG (wild-a**-guess).