The first issue is indeed that the wrong interwiki has to be removed on _all_ languages to stop it from returning, but even with that one could still get into problems because there might be bots that visited some languages _before_ your removal, and others _after_ it. They would then consider the wrong interwiki to be a missing one on the languages visited afterward, and re-add them there.
commenting out interwiki links like <!-- [[en:Wrong iw link]] --> prevents bots bringing the wrong link back
Greetings xqt