Major Stuttering on First Channel Before Switch - DVR Affected

Have had a problem with my service for about the past three months. It had been working fine for the year prior, then all of a sudden we had an issue where the first channel after turning on the box would have massive video and audio stuttering and pixelation. Generally, it remains on that channel - you can switch to another channel and it comes in fine, but then back to the first one, it's still messed up.

One of the unfortunate side effects is that it's made DVR recording extremely hit or miss, since if it's on the broken channel the recording will break, and the channel that's broken keeps switching.

Resetting the box through the settings menu (getting the ping-back to the box) helps sometimes, but the problem keeps coming back.

I've had multiple chats with unhelpful, greedy Verizon techs who want to charge me upwards of $40 to come to my apartment (it's an apartment building, so I have no control over the wiring!) I've sent the STB back and gotten a new one, but the problem still exists. I've tried switching out all the coax (it's a very short run from the STB to the wall adapter with one splitter), I've switched the splitter, I've bought some attenuators - no luck. The problem goes away for a week or two sometimes, but it always comes back.

For the past three months we haven't been getting the service we've paid for and it's silly for us to keep paying if there's no help - but it's also silly to charge for a problem on Verizon's end, not ours (when we're already paying $100 a month!). It's one of the most frustrating customer service experiences I've ever had. What can we do?