Looks like I might be replacing my 4 day old unit. The OTA tuner is not working well. Only one of the two OTA tuners has ever worked, and since yesterday I cannot tune all the local OTA channels anymore, but I could the first 2-3 days. I show good OTA siognal strength, it just on't tune the programming on all the channels. After much troubleshooting they are sending a tech out in a couple of days to look it over - I hope he fixes it and/or brings a replacement with him.
Another thing to consider is nearly all OTA tuners are still having problems with multipath distortion. Usual things to check include: ensuring the antenna is as close to the towers as possible if indoors, tweak the left/right and up/down of the antenna, ensure that all splitters with empty ports are terminated, you've haven't over amplified the signal, you don't have an FM station stomping on the signal, etc. While I have a lot of experience telling OTA problems with the HR10 by looking at the signal meters, I haven't had any problems in my current home so don't know how the HR20 responds, alas.