This might sound initially like a too-clever undergrad ‘gotcha’ paradox. However, I think that at least for some folks who have perfectionist tendencies, the following is experienced as a genuine difficulty in their lives.
The following strikes me as plausible:
(1) It’s OK to make some mistakes.
If (1) is true, then it seems the following should be true as well, since it’s just a restricted version of (1):
(2) It’s morally OK to make some moral mistakes.
(3) Making a moral mistake is doing something morally impermissible,
(4) if something is morally OK, then it is morally permissible.
And (2)-(4) logically entail
(C) It’s morally permissible to do some morally impermissible things.
And (C) looks like a contradiction.
(For all I know this is already out there somewhere, but it was not on the interesting list of paradoxes of deontic logic in the Stanford Encyclopedia.)