Crate GFX212 Volume issue

[blues harp cat]

Hello everyone...this is my first post.
I'm having an issue with my Crate GFX212 amplifier...the volume level intermittently does not work... there's no crackling when I turn the knob... lately the only way to make it work is to turn it up and down over and over again, although lately that doesn't help much. I've noticed that it does sometimes start to work when I unplug the effects loop that plugs into the "INSERT" which may be totally coincidental.
I'm pretty much a DIYer, but it's no doubt quite obvious that I'm a noobie as far as electronics go...
Any ideas would be greatly appreciated...

[Jazz P Bass]

Run a patch cord from the FX in to FX out.
If the contacts are dirty you will get no sound without a patch cable.