Internet bandwidth just stops every few minutes for 10-20 seconds. For months. Already had a Cox technician replace the cables throughout the house. How do we fix this?

I float back and forth from Cox to CenturyLink DSL every year or so. Cox is typically much much faster but it's so inconsistent that I end up leaving for slow but highly reliable CenturyLink. I'd love to just have Cox fix this issue where every few minutes, all day all night long, my internet just pauses for 10-20 seconds every few minutes. This often does affect my streaming and unable to watch a show without several buffering issues (nothing else going on in the house bandwidth-wise and I have the "Ultimate" package). Online gaming? Forget it.. impossible with Cox.

I'd be willing to pay cash money if Cox will fix this issue I've had - I'm using all a Cox pano router, all cables provided from Cox, I'm in the IT industry and have tried everything I'm supposed to do on my end.