This also happened to me locally, and I came up with the same fix, it looks good to me.
I attached a tap test I used fo reliable local reproduction, as in was a very unlikely failure in the existing test cases (~0.1% chance). We probably don't want to include it in the normal test suite because it is quite specific, but it is useful to verify that the issue/fix exists and works.
nofcbot-0001-Add-deterministic-test-for-concurrent-seque.patch
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