I'm not good at waiting. If it was a big problem I'd just exchange the box at the "local" office 30 miles up the road. The problem with a service call is if they determine it's your problem then you get the bill. OTOH, if it gets fixed then maybe it's still worth it .
Could be it's poor signal strength. They should have been able to remotely look at what the box is reporting without damaging anything.
Do you have cable Internet? If so, you can usually get signal strength from the cable modem. It's not a guarantee what the STB sees, but if it's way out of whack it could be a clue. Type 192.168.100.1 into the address bar and hit enter. That almost always brings up the cable modem stats page. What are the numbers (screen capture works well)? Example:
View attachment 886285
You don't, by chance, have the cable box stacked or in a relatively tight space so it's not well-ventilated?