Losing access to certain sites and port forwarding rules.

The problem: I will randomly lose access to specific websites, and my port forwarding rules.

 

It's the same websites every time.  Any example of one of the websites is https://canyouseeme.org/

There are other websites, but I work tech support form home, so most websites I frequent and notice this happening with are company websites. But the example above is not one of my company websites. 

Some of these websites I'm accessing are located in the US, and some are located overseas. 

This will happen seemingly randomly. I've not been able to notice any event that is triggering this.

The moment I reboot my router, I will have access again to all of these sites for an indefinite amount of time until it happens again at which point I will reboot my router again and the cycle continues.

 

In addition to this, when I lose access to this website I also lose all of my port forwarding rules. I have a handful port forwarding rules configured on my router, that I configured through the portal online on the Xfinity website. I use these ports to access several different services located on my home server. I will be unable to access any of these services remotely as my ports will be closed. An online port scanner will show them as closed. Rebooting my router will return all my rules back to normal, and I will again be able to access my home network server again remotely. 

 

I have the Dual-Band WiFi router  XB3 that I've been renting. 

I've gone through about 4 of these routers in about 2 and a half years. I've had this problem with every single router. 

It will not be at first. Usually the replacement router will last a few months before these problems start happening.

 

I recently moved at the beginning of June. I kept with me the router that I had from my old place. After 2 weeks in my new place the router (that I've had for 6 months prior) started presenting these problems again just like previous routers had.

However, this time it was worse than ever. The problem was reoccurring every 20-30 minutes. And the number of websites that it was affecting had doubled. 

Talking with Comcast support on the phone (each time previously they had just set me up with a new router) this time around they said they were going to send someone out to check to make sure that the installation was done right in my new place (it had never had services here before).

The tech did his thing. He said that my router had "really bad signal strength", and he replaced my router with a new one.

This new router didn't last a day before the problems started up again. It's not as bad as the before. It's only happening maybe once a day now. But it's still very fustrating to deal with. 

 

Does anyone have any idea what is causing this? 

Does anyone know how I can fix this? 
Are these routers just notorious for doing this? 

Do I just need to stop renting these routers and buy my own? 

 

Thank you.