GPU temperatures climb up slowly until 70C - not sure what to do

Right now, the loop is as follows: reservoir > pump > radiator > CPU > GPU > back to the reservoir. The GPU block is from Bitspower (For the Zotac AMP Extreme!), and the other water cooling parts are from the EKWB X360 kit (I swapped out the radiator for the 480 one). I spent a bit of time trying to get as much air bubble as I could out of the system, reapplied some thermal paste on the GPU, and re-applied the thermal pads that came with the block.

However, when I play Doom and let the character stay still, the temperatures will climb up from 40 to 70 in around 2 hours - I am not too sure if it can go higher, but that's how long I tested it for. The CPU all the while seems to be OK - temperatures during load (Not OC'ed) range from 50-60, but this is not OC'ed, so I'm not quite sure if these temperatures are good enough or not.

Obviously there is something wrong with the GPU. Are the temperatures for the CPU okay? Also, what are some possible solutions? I've ordered an extra thermal paid (50 x 50 x 1.5mm) to cut up and replace the ones in the card, and plan to also replace the thermal paste just in case.

EDIT 1: I tried to see if there were any large air bubbles trapped inside the radiator, and nothing changed.

EDIT 2: Also, because of these intensive tasks, after I close them, the temperatures will stay pretty high. Right now, my CPU is at 50C, while the GPU is at 47. Could it be the pump?

EDIT 3: I changed around the tubing. Will take a picture later, but I was able to shorten the tube length between the radiator and CPU, and also change the angle so that the liquid goes directly down from the reservoir into the pump. Lastly, I changed it so that instead of going down and back up to the reservoir from the GPU, I used the other "outlet" from the GPU block so that it comes slightly up, but goes down at a much more reasonable slope to the reservoir. Overall, the flow seems to have improved greatly.

Unfortunately, the temperature problems still persist. I'm thinking that the pump is the culprit here. I will see if Microcenter would be willing to swap it out for a new one, and will report back with my findings.