As MD5 Self Signatures are ignored nowadays there are keys that do not have a valid self signature on their uids
Those keys can be imported with --allow-non-selfsigned-uid but in Kleopatra this is not really visible. Only in "Details -> Certifications" can it be seen that the self signature is invalid.
Kleopatra for example offers it to try to certify such a user id but that will then fail with "General Error"
Underlying the General error is:
User ID "Foo Bar <email@example.com>" is not self-signed. Unable to sign.