Digital Signals cutting out with Adcom Preamp

Hello gang. I recently purchased an Adcom GTP-880 Pre-amp and I'm having issues with it staying locked in on digital sources. On analog sources it's fine but on digital sources I might get a 10 second cut-out where the unit switches back and forth between "locked" and "unlocked" before coming back.

This only happens on digital sources. Am I doing something wrong?
If you are using Toslink interconnects,make sure its plugged all the way in.If your using the RCA wire interconnects, check their connections too.If your new to Toslink,they have about 1/4" travel to fully seat,also they (Toslink) ends usually ship with a little soft plastic protector cap easy to just slide of the ends.That could cause a problem like that. Don't force though. Maybe somebody else might be of more help.