I also have a RX 5700 XT RED DEVIL POWERCOLOR, purchased in June 2020, the junction temperature three times reached 775º C, and the current temperature was 41º C, unfortunately AMD RADEON, did not answer me when I mentioned in e- mail this eventuality. Is 775º C a bug in the AMD RADEON SOFTWARE ADRENALIN 2020 program?
At 775c (1427F) the board would have caught on fire and turned to ashes
I don't believe it is a bug in AMD Radeon Settings otherwise there would be many other reports from Users complaining about the same thing.
If you use a different GPU monitoring software to check your GPU temperatures and you get the same results then it probably is your GPU card.
Sounds like your GPU card may have a defective Thermal Sensor on it.
I would open a PowerColor Support ticket to see if your GPU card needs to be RMAed to be checked or replaced.