We have a SVG2482AC modem/router and everyday upto 3 times a day or more telephone 1 slowly flashes. I also found out that it could be either a bad phone jack, or bad wireing inside the house causing the problem. When it does this we can call out but anybody that calls us we can hear them if we answer it but they can't hear us. Does anybody have any advice for how to fix it? But weirdly if you have xfi you don't get this issue because of their modem/router which costs $11 a month!
It certainly sounds like you have a short in your phone wiring somewhere. When the tel light starts flashing like you say it is it is signifying the line is currently off the hook. I would look around and check all your phone jacks for corroded terminals (they will be green or black) to eliminate the obvious. Typically you will have more issues when people call in then when calling out due to the line raising the voltage on inbound calls to make the phones ring. When the short gets bad enough the line will simply cut out anytime someone calls.
Have you noticed any static on the lines by chance? It is also worth mentioning if you had one of the Comcast modems and encountered a line short you would be having the same exact issues.