My Gigabyte RX 5700 XT Gaming OC had some very high HDG and JUNC temperatures (80-85C and 110C consistently respectively under load while playing games). As it was a little over 3 years old and my warranty expired I decided to change the thermal paste and pads with 0,5mm and 1mm thickness (Gelid Extreme).
The GPU always ran hot since buying it but never hit 110C JUNC temperatures.
After reapplying my HDG temperatures are a tiny bit lower (80C) but my JUNC temperatures are still too high (110C). I know the GPU is throttling as my FPS in Halo Infinite is only 50-60, Anno 1800 at 40-50, BF-V at 80 FPS (1440p / high settings which were fine a year ago with much higher FPS).
Gigabyte does not want to share the official thermal pad thickness but online I found it was 0,5mm and 1mm. And after checking it looks like the new thermal pads do make a good enough contact (see picture). The thermal paste also spread nicely (used X-pattern and it completely filled the GPU die).
So now I'm honestly a bit lost what's causing the high JUNC temperatures. The only thing I can think of is something odd I saw on the GPU die. There was this one spot that I could not clean no matter what I tried (see picture). Could this spot be the culprit?