It's the RF cable from the STB to the DVDR. Make sure it's of high quality, and wrench tight on both ends. Not those push-on types of cables. If it's not the cable then either the STB is sending it out bad or the DVDR is receiving it bad. To eliminate the latter, try running the cable straight from the wall to the DVDR. If the problem persists then either the incoming cable signal has the problem (call the cable company) or the DVDR is receiving it bad. Eliminate the incoming cable problem by running the cable straight from the wall to the TV, if the problem persists the incoming cable signal is bad.