I tried booting the agl-kvm-demo-platform image on the AGL reference hardware to vet some recent changes, and native-shell-client or QEMU seems to be tickling something in the newer agl-compositor in Octopus and master, as it throws an assert:

Apr 25 21:02:57 h3ulcb agl-compositor[1047]: agl-compositor: ../weston-10.0.2/libweston/backend-drm/kms.c:1403: atomic_flip_handler: Assertion `output->atomic_complete_pending' failed.

This results in a bit of a mess with it aborting triggering coredumps from the QEMU instances and native-shell-client, which systemd then attempts to restart, so the whole process iterates.  The coredumps don't really provide much more information to my untrained eye, but I can try pulling something our of a agl-compositor one if you can tell me what to look for.