Frequent short sound drops and picture freezes in cable TV

For the last month or so, I've been frustrated by frequent short (3 - 5 second) sound drops and picture freezes. I'm in Lisle, in the western suburbs of Chicago. It happens on every channel, but seems to be particularly present on channel 191 (PBS station WTTW). Resetting the tuner makes no difference. The signal strength (75% - 90%) and signal quality (100%) are well within requirements. I was watching a PBS program at my father's home in Wheaton last night, and the exact same audio drop picture freeze problem happened there. That's about 20 miles away. My brother, in Naperville, (5 - 10 miles away) reports the same problem. So we have multiple customers in multiple western suburbs all getting frequent signal glitches from Xfinity. Why is this happening? How many other customers near Chicago are seeing these frequent short drops?

The customer service web page provides no way to report this type of problem. You can only say service is completely out. You can't report short drops in TV service.