https://bugs.freedesktop.org/show_bug.cgi?id=102322
--- Comment #86 from Paul Ezvan paul@ezvan.fr --- I was also impacted by this bug (amdgpu hangs on random conditions with similar messages as the one exposed) with any kernel/mesa version combination other than the ones on Debian Stretch (any other distro or using Mesa from backports would trigger those crashes). This was on a Ryzen 1700 platform with chipset B450. I had this issue with a RX480 and a RX560 (as I tried to replace the GPU in case it was faulty, I also replace the motherboard).
I was still impacted with Fedora 30 with recurring GPU hangs. Then I replaced the CPU/motherboard with a Core i7-9700k/Z390 platform. Since then I did not have a single GPU hang on Fedora 30.
My hypothesis on this problem not being easily reproducible is that it would happen only on specific GPU/CPU combinations.