Have you tried configuring your Ryzen CPU Fan using Master Ryzen?
What CPU Cooler are you using? Wraith or some other cooler?
I had something similar happen to my AMD FX 8350 CPU. While idle or light it would go in the low forties to high Fifties. But when the CPU went over 50% usage on all cores it would climb above the Sixties and eventually shutdown from Overheating when it reaches 100% usage if running longer than a few minutes. I replaced my CPU Cooler (about 5 years old - Stock version) with a much more powerful one (Cooler Master 212 EVO CPU Cooler). Now when my CPU goes to 100% the highest temperature is 59 degrees centigrade and stays there. I verified this using diagnostic program OCCT and other temperature monitoring software.
I would go with Master Ryzen's temperature readings since they will be the most accurate. Core Temp is good for estimating temperatures. Core Temp has a option to use Offsets to bring the temperature closer to what other programs are indicating. I have a 8 degree Offset to show temperature relatively close to what other programs are indicating. Your will have a different Offset for your Ryzen.