Xfinity's internet box loses connection every 30 minutes or so between the hours of 8 am EST and 9PM EST

About a month or so ago we get an email from Xfinity saying that they are "doing things to improve our connection" or something along that line. Ever since our internet would go out between the Hours of 8 AM EST and 12 PM, and recently that time span has grown and now happening at around the hours of 8-9 PM EST as well. We are unable to get ahold of a person, because their cellular and Email bot that you MUST TALK TO will not direct us to a human, and even when we do get far enough, it wants to "schedule an appointment", at which if our internet goes out and comes back their bot proceeds to "Automatically remove your set appointment because your internet seams to be working now", and when we did have a "tech" out here they said, and i quote, "We can not really do anything unless the internet is already down and having an issue when we arrive."

Customer service issues aside, we have been unable to get our internet stable. resetting the modem/router does not help, YES the cables are tightly connected, internet speed is fine when it is working, and the cables are brand new and have been working perfectly before they sent out that email about "Improving our connection". The modem has a white light when there is internet and it blinks yellow when its not connecting, blinks green when its re-obtaining its connection, and white when its connected. Furthermore, the internet goes well before the modem even knows there is an issue as we lose connection before the white light even goes yellow, and then once it becomes yellow, it reconnects in an instant, only to go out again in about 10-30 minute intervals with no actual consistency but the time periods as to which it happens, although, as of recent, even the time frame to the outages have been fluctuating as of recent with them either happening earlier, or lasting longer, than before.

The closest "office" that we can physically visit is a 3 hour drive, and we will be not driving that long/far unless we absolutely know its not going to end up a waist of time, money, and fuel, and as previously stated, getting a hold of a live body is next to dam imposable. Everything here runs on and needs the internet which is why we have the Gigabit plan, and we can't pay our bills without the internet due to the main money maker of the house working from home through a VPN to connect to the workplace, and no, the VPN cannot be the issue because if a VPN was an issue that would not explain why the modem is dropping connection and not just their computer as the VPN is not in the modem/router its on the PC they use to Work from.

any help will be greatly appreciated, due note, we have done ALL of the basics, just didn't mention all of them here as we've been through all the basics that internet companies tell you to do before, "do you have a bad cable? did you restart the router/modem? did you unplug it and plug it back in?" and so on...