Thank you for quick response)
I couldn't build and test 2.1.9 right now, but bug is still here in 1.4.16 and
2.0.22.
I've created test script for this case:
https://gist.github.com/anton-ryzhov/a0dcfcaabe18fc6ad35e
Run ./gen.sh in some working folder and then try ./runtest.sh several times,
expire different subkeys, compare the result.