What are some of the signs of a dying receiver?

Over the last few weeks, one of my active HR20-700s has been doing some weird things. I'll preface this by saying it sits alongside a couple other HD DVRs in my living room: another HR20-700 and an HR24. They all remain on and not powered down or on power save mode.

While sitting in my living room watching TV, I noticed the front circle of lights on the HR20-700 in question (the least watched of the 3 boxes in that room, BTW) would act funny. There would be a triangle of 3 of the lights on it begin to flash, not sequentially or like the circle of dots when one uses the DVR functions; rather, this 3-dot triangle of blue LED lights on the front would suddenly flash off and on for a while. When this was happening, the DVR would be rendered inoperable--none of the functions worked. Then, the thing would reboot and all would be back to normal.

I had never seen this before on any of my DVRs (HR20s, HR21s, HR22s, and HR24s), and this has been happening on only this HR20-700.

Last night, I get home and turned on the Steelers-Bengals game, which was being recorded on this DVR on my local NBC channel. Well, double play was working, so I switched to the tuner on which the football game was being broadcast, and I got a black screen--no video or audio. However, I could get the banner info and orange, recorded buffer bar up. Switching back and forth or even going up/down to other channels didn't matter. The problem still existed. The channel of the game was simply not viewable.

These two main problems have recurred more than once over the last few weeks. The DVR is not young, of course. I still have it because I love to use its built-in OTA tuner. I'm guessing I got this thing at least 5 years ago if not earlier than that. It could even be 7 or more years ago; I don't know exactly.

I don't think I'm having other problems with it save for these two main ones, but they are recurring like I said.