SPDIF keeps cutting out

Have been using the same setup for over a decade now. The spdif recording has started cutting audio randomly for a moment. I know it's the spdif since everything works normally through the analog outs. I also can see loss of sync from the Lynx mixer panel once in a while.

Soo, how would I find out if it's the Kemper or my cables that have gone bad? The cables cost 150 euros so I'd rather avoid buying them if it's avoidable.

I think I got it hopefully solved. Maybe it was just dust/dirt from over the years, cleaned the contacts from the cables and it stopped cutting out.