Further testing suggests that the problem is caused by the kernel not having enough time to settle after partx -u exits (race between acknowledging the new block device and actually having it available?). Adding a 1s pause after the partition table is re-read seems to prevent this crash.
Further testing suggests that the problem is caused by the kernel not having enough time to settle after partx -u exits (race between acknowledging the new block device and actually having it available?). Adding a 1s pause after the partition table is re-read seems to prevent this crash.