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