Adding Clef to Instrument Change = Crash

Hello,

I am working on a multiple percussion piece and have the part switching from cabasa to vibraphone. While the Vibraphone does produce the notes in Ab Major, it doesn't show the key anywhere. When I click on the measure where the vibraphone starts and add the Ab Major Key Signature, the program crashes. I have switched it from the percussion clef to treble clef and tested it that way but received the same results. What's weird is that it shows in the other 2 mallet parts, just not this one. Is it because it's originally a percussion clef?