The idle temp is high-ish but 65C max load temp is not too bad.
The HSF mounting or thermal paste application might not be quite right and impeding optimal heat transfer.
But would an incorrectly applied paste/HSF mounting cause the problem?
My concern are 2 things -
1. Unusually high idle temp - roughly 30 degrees above ambient
2. Absurd fluctuation of temp while running prime 95. Regularly oscillating between circa 50 - 65 C. You can see that the graph is pretty much a sin/cos graph. A standard prime 95 stress test would yield something similar to a logarithmic graph like this (I tried with my own PC)