@julien-f Hmm, that's a bit disappointing that there isn't much you guys can do to help. No worries, I'll keep testing. My AD environment works fine, since the accounts in question are not locked and are being used daily. The only place they're failing is in XOCE or XOA.
It's gotta be something with how the library is handling characters in either the username or the password. I'll keep testing until I can find a repeatable pattern.
Thanks to both you and @olivierlambert for the help thus far.