XB8 keeps randomly rebooting itself.

I have the Technicolor XB8 CGM4981COM

I've had an issue with the past 3 boxes here. They randomly reboot a few times a day or go a few days without doing so, then it happens again. Sometimes it's 3+ times a day.

The first XB8 i had worked flawlessly and I received the full Gigabit I pay for, until about 2 months ago, then the issue happened. I thought it was the box, so I called Customer Service and they sent me a new box, unfortunately it was an XB7. It worked fine for a day and then the issue started again. I also only received half of what I paid for with that box, and the realtime game I played was very laggy consistently. I returned that box last week in store and asked for an XB8.. It instantly brought me back to a gig, worked fine for an hour then reboot twice. Figured it was because of an update so I ignored that, few hours later it happened again so I called. They said they see no issue and to give it a few days. Well it's been a few days and it's reset a solid 8 times since. I called last night and they ran a test after I told them this story and said everything looks perfect, so they're unable to schedule a technician because they don't have the option since it looks good on their end. So what do I do?

This place is built in the 70s and we've been a customer for 13 years. I live in a Manufactured Home so my coax hangs out of the wall. I have a feeling there's an issue with the line outside since I've tried 3 boxes and all 3 have the same issue. To clarify, the line coming out of the wall is directly hooked into the XB8.

Side note, I don't want to push but I want this resolved ASAP if possible. AT&T is installing Fiber in my area since the last 2 weeks and if I can't get this issue resolved so I can use the internet without being randomly kicked off daily, I'll have to switch providers. I don't NEED fiber, so I wouldn't switch if this gets fixed, we've been loyal for 13 years, what I have works perfectly.. When it works. But like I said, if I can't get this resolved I'll unfortunately have to make the change. Please help me resolve this issue so I can continue to be with xfinity and hopefully make it to 20 + years.