Intermittent sound problems

I've set up using a pi4 with usb grabber and switch after not having everything setup for several months and I'm getting sound drop outs both when watching sky and also when watching anything on firestick 4k max. It's happening when led's arent even switched on and does seem to happen more often watching sky than firestick. I should mention all external devices run through my denon amp which is the same as when i had it setup before and don't remember this being an issue then.