What version of MuseScore are you using? For me, with both 2.0.1 and a recent development version, there's no problem with that key signature at all. If problems persist, please post an example of a score you're having problems with and precise steps to reproduce the issue.
I am guessing your staff is for an instrument that uses "Eb" transposition, like alto or baritone saxophone, in which case this is normal and correct behavior. You have to add key signatures at concert pitch, because otherwise, it would be unclear what you mean if you score contains multiple instruments.
Comments
What version of MuseScore are you using? For me, with both 2.0.1 and a recent development version, there's no problem with that key signature at all. If problems persist, please post an example of a score you're having problems with and precise steps to reproduce the issue.
I am guessing your staff is for an instrument that uses "Eb" transposition, like alto or baritone saxophone, in which case this is normal and correct behavior. You have to add key signatures at concert pitch, because otherwise, it would be unclear what you mean if you score contains multiple instruments.
I guess Marc guess is spot on. No news for 3 years. I close this bug.