Internet connection keep Bouncing (disconnects and reconnects many times consecutively)

For the last year, I had and Xfinity Modem.

During this time, the internet speeds would nit be able to maintain more than 1 device streaming data (Video services, Games, And other applications).

To remedy this, I purchased my own Motorola MB7621 Modem. This fixed the issue for about a week.

I verified, and we were able to stream on all of our devices simultaneously without any issue.

After about a week, we started getting intermittent connectivity issues in all of our devices, regardless of what we were attempting to access.

The devices that I have:

Xbox One

Playstation 4

Smart Tv

Work Laptop

2 Desktop PCs

3 Android phones.

Every time I have had to call Comcast, they insist on a Modem and router reset.

After 3 more months, one if their CSRs told me that my Modem wasn't compatible, so I switched back to an Xfinity Modem, and the issues are still persisting.

I have had 2 onsite techs replace the cable from the Xfinity box to my modem, and replace the splices on the line. The second tech was still onsite when the internet dropped again, and has told me that he put in a work order for one of their advanced technicians to investigate the ground line and box on their end, but its been over a week, and I haven't gotten any updates. Meanwhile, this issue is so bad that I haven't been able to work at all in almost 2 weeks.

I've investigated other ISP options for my area, but they don't provide service to my apartment for issues varying between "can't aim the dish to the correct orientation", all the way to "the phone lines in the building won't carry enough signal."

I don't know what to do, because this issue is putting me in a place where I am about to lose my job, and because if health and financial issues, I'm not able to do work that isn't remote.