Normally, I would say the problem is that the receiver is an RCA, but I'll be technical here.
Check the wiring on the speakers for shorts -- is there any bare metal touching any grounding surfaces? Then, check the wiring on the speakers for closed loop shorts -- is there a "ding" in the cable that would cause both leads of the cable to directly connect?
Finally, try disconnecting each speaker one at a time to see if the speaker possibly has an internal short, of if there is a short or closed loop short within its respective wire. Disconnect the speakers from the RECEIVER end to test for bad cabling. Disconnect the speakers from the SPEAKER end to test for bad speakers.
If the receiver still does this after testing it, the receiver likely has an internal issue.
To test the receiver for internal problems, change the source and try it. If it doesn't cut out on for example, FM, then its not likely the receiver.
Try also connecting the DVD player to a different input and see if it still does it, if it only does it on the DVD player. There may be an issue on the line between the DVD player and receiver.
If you are using a single coaxial SPDIF cable (one RCA cable) to connect your receiver to your DVD player, try swapping that cable out. There may be an internal issue in that cable, or there may be interference nearby. Try also relocating the path the cable takes to the receiver.
This is the amount of jacks I have on my receiver:
I know how bad a short in one cable can be to track down...
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