Any time I've loaded something into the trunk of a Waymo, it pre-emptively pops the trunk when I'm getting out _for_ me and reminds me to get my things from the trunk, so this is... surprising as a failure mode. Wondering if there was some issue with the latch/opening system, because it's definitely programmed to work the right way. (Or he tossed his stuff into the trunk from the main cabin, but... it's a pretty low hatch ceiling there.)

None of that is the problem, shit happen, the problem is them asking them to come get their stuff instead of apologizing and sending the luggage at their own expense with a free ride at a future time.

They seem to have changed this recently, possibly due to theft or items falling from the trunk.

My last two trunk-use rides have had closed trunks on arrival.

Not that surprising if the thing that failed was the thing that notices whether or not you put something in the trunk in the first place. Unless it does that routine at the end of every ride, regardless of whether it thinks something is in the trunk or not, then it's not a fail safe system and occasional mishaps like this should be expected at scale.

Over hundreds rides I've found it's extremely flakey on if the trunk will open again at dropoff after opening it earlier.

My guess would be the Jaguar's CAN bus being the weak link