Note: Run with --repeat=N if it's not reproducible right away.
The test case above kills a connection in the process of creating a sequence. Expected outcomes are that the sequence either doesn't get created, or is fully functional. However, most often it's created, but remains unusable, attempts to refer to it end up with ER_KEY_NOT_FOUND:
It fails nearly every time for me, but it's still a race condition, so sometimes it misses the mark. Run with --repeat if it doesn't fail for you.