PC freezes and recovers quite often

Hi, I'm new to this site so please let me know if I should post this in a different section of the site. I built my PC just over a year ago and have done quite a bit to it. My issue is, after delidding my CPU and installing a custom watercooling loop I started having issues where during gaming and being logged into discord, approximately once an hour my PC will freeze for about 5-7 seconds and then recover. Sometimes everything is fine afterwards, sometimes I get partially disconnected from discord and have to leave the channel and re enter it to be able to use it. I'm not sure if it's something that happened during the delid, the used GPU I bought from a friend, or if it's possibly a motherboard issue. My build is as follows:

Fractal Design Define S Case
Asus Rog Strix Z370-E Gaming Mobo
Intel i7 8700k delidded(liquid metal)
Asus Rog Strix GTX 1080
EVGA 1000w PSU w cable mod cables
1TB Samsung m.2 SSD
1TB Samsung SSD
6TB WD HDD
EKWB GPU waterblock
EKWB CPU waterblock

Any and all help will be greatly appreciated, I'm to the point where I'm considering replacing costly components.