Sorry I just saw your question. I didn't notice it over the past couple days but this thread has had several comments.
Ryzen Master always shows the temp as much more consistent and doesn't ever show the temperature spiking fluctuation. Most the 3rd party apps show per core temp fluctuations like core temp, hwinfo will jump around a lot from one second to the next. When Zen 2 first came out core temp was way off IMHO in reporting temp. Then AMD came out and said that 3rd party apps would need to be updated as the way Zen2 reports temp is very different than earlier architectures. I would imagine that with those changes that even with updated apps that are now supposedly Zen 2 compatible that it still may not be measuring, polling or averaging the temps even in the same way that AMD is in Ryzen Master. I don't put too much worry in these apps numbers beyond if I was to start seeing a change that was not normal for my system and then I would go to Ryzen Master and see what is really happening according to AMD's software.
The OP reported they were seeing this fluctuation in Afterburner. I see it in Core Temp and HWINFO myself, but don't see it as abnormal as temps are always way under thermal limits.
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