groupby64 snapshot-update-status:snapshotted
I don't know what "snapshotted" means.
groupby64
current-slot:a
slot-successful:a:no
slot-successful:b:yes
I believe this means that the bootloader believes that an update is in progress, from B to A, but believes that A has not successfully booted.
I think that in theory after some number of attempts to boot A without success the bootloader is expected to switch back to B. But I don't know how many that is, nor do I know whether "snapshotted" might be a problem.
You might try letting it bootloop for a while (maybe 30 times?) to see if it does switch back to B. And maybe a developer will comment.