Bug#1060121: mdadm: Value "XXXXX:0" cannot be set as name. Reason: Not POSIX compatible. Value ignored.

[Bogdan Voaidas]

I have the same error.
2 identical servers with the same os and configuration but one has
mdadm - v4.2 - 2021-12-30 - 14 which gives this error
the other
mdadm - v4.2 - 2021-12-30 - 8 doesn't give this error