As an example of the issues I am having I was just away from the TV for 10/15 minutes and when I came back the channel I was watching (CBS 42) was frozen. I used the swap button to switch to another channel (Fox 6), I use PIP a lot. It was blank for a couple of seconds and then came in.
I had the same loss of locals issue a few weeks ago although signal strength was high. Was out for 15 minutes that I'm sure of but could have been longer. Has been fine ever since? Never found out what caused it.