Recently we had my Spectrum Business internet connection go down. No matter what I tried it just was not coming back online. My router log showed daily outages varying from a few seconds to 15 minutes. I complained about it but nothing got resolved by Comcast / Spectrum business cable. Finally they had send a technician who checked the line and replaced their modem/router combo and left.
One they the internet connection permanently failed. So I called tech support again and spoke to a very knowledgable technician who figured out that the old modem/router combo had been installed in an other location still using my static IP address!
Rather then sending the modem back for inspection and reset the technician must have kept the modem and connected it for an other client without even bothering to check the setup witch he could not have done since I always change the default username and password. Once they reset the old modem to factory settings therewith bumping the new client off line my internet connection came back a live and has been stable.