I've been using an A&H Xone22 for a few years and recently it's been doing something where the volume swings up and down while I'm playing. It will go from quiet to loud and it's quite jarring. Since it happens on both my turntables and through both channels I'm assuming the issue is the mixer. The VU meters don't show any variation when the volume dips so I'm guessing something is going wrong with the output. It happens through both the monitor out and the master out.

Anyone have any idea what kind of repair I'm looking at? Reasonable price range etc.
Hoping it's not time to require this mixer quiet yet as I'm pretty fond of it