modem errors

Lots of erratic speed issues.  I pay for 300Mb speeds and, mostly, get it... but there are times when everything stops entirely.  I just captured some screen shots showing extreme modem errors after doing a complete reset at 9:21AM.  In less than 8-hours the accumulated errors are HORRIBLE!!  I could go for weeks and weeks with this NEVER happening before.

Hopefully, someone who knows what they're talking about can answer my questions... I actually had a phone operator argue with me that there was "no way I could be getting speeds above 300Mb", even though I had recorded history of well over 360Mb on average.  It blew me away that customer service would argue with me that I was getting something BETTER than what I was paying for.  

I so wish we had an option other than Cox.  I've been with them for 18+ years and am so tired of this...