Yes, I'm trying to re-subscribe with the same list of user-ids, that has not changed.
The re-subscription have been working for months with this list.
At new years-eve, one of the user's account((e7c5bd5e-494e-469d-850d-b7c8c03545a5)), part of the list got disabled.
However, the re-subscription still worked until last week when the response was 500 InternalServerError.
Apparently there ia a grace period within azure AD on user accounts and therefore the error response got sort of "delayed".