What could possibly be hurting my signal???

•Gigablast plan
•Brand new coax running through my home.
•Only 1 splitter (cable modem/TV box)
•Docsis 3.1 modem. All levels power and SNR levels within recommended.
•Lines tested at home and at road by senior technician. Says everything looks great.
•Technician ran a ping plotter to determine of any nodes were bad. Everything looked good.
•All wiring and connectors are secured firmly.

My issues: connection inconsistencies

I can have a short span where everything seems to be going well, then BAM...lagging everywhere.
I don't have a pc so I can't particularly run these advanced pc tests. But from what I'm observing, my biggest issues are PING SPIKES, PACKET LOSS, AND FLUCTUATING UPLOAD SPEEDS..

I'm also getting T3 TIMEOUTS in my event log

I started to think maybe it was the servers I was playing on and not my signal.
But I play at my girlfriends house and have absolutely no issues. She has suddenlink.

What in the heck could be my issue? Because cox is not able to detect it and I find it very annoying to not even be able to game on gigabit speeds.

Ps: at this point I'm testing things straight wired to my modem. Is there anything that can be interfering with my signal that cox wouldn't be able to detect even with a ping plotter?

I need some real knowledge here.