Question Packet-loss to default gateway only on one PC at night (wired + wireless) ?

[repofmady]

I have had packet loss issues whilst playing rocket league for a few months and decided it was to do with my ISP, however when running pingplotter on a different pc (on wifi) it was completely fine. saw online to ping default gateway and i'm getting the same bad packet loss, however it only happens from 8/9pm, to 1/2am, and it's the exact same on both wired and wireless, one person i talked to says it might be a bad network card? appreciate any help thanks