Help: G String Issues

Hello, I’ve recently gotten my first Ernie Ball Majesty 7-string. Absolutely love the guitar so far aside from the issue I’m having. I’m tuned to drop g with 10-56 cobalts. The intonation and bridge are all set up and everything plays fine and stays in tune except for the G string. Bending or using the whammy bar causes it to go sharp or flat. I’ve tried putting some graphite under the string on the nut but no luck. Any suggestions?? Would upping the string gauge help? I’d like to avoid that if I can because for the most part it plays beautifully currently.