Check your firmware version https://www.tp-link.com/us/support/download/archer-c7/#Firmware Be sure to use the correct version number. Some things to check. Power off modem, router and PC. Power up is sequence. If you still have an issue, connect the PC direct to the modem, bypassing the router and test. If you still have an issue, it is not the router. Check the modem logs for critical errors. Generally a router does not work great and then start have intermittent issues. What changed about the time the issue started. Since you have Spectrum, anything change with your TVs and such as a new one or removed one as it shares the same signal line as the modem.

@MOB27 

 

Where/what 'is' the instability? Instability can be many things, so knowing what it is might help here. IS it seen on ALL devices?

 

Wireless can be caused by many things, so this is an important question. From your initial statement of a 'wireless' network, are there wired devices in use? Do they also exhibit the problem?

 

Of course, the other question, what was changed when this started? Devices added, usage changes (more streaming, more game play), or even ISP service changes?