Linux - "Error in UE4Editor free() invalid pointer" when using amdgpu driver

Hello,
I have the problem that, when trying to run UE4 using the open source AMD Drivers, I always get “error in ue4editor free() invalid pointer”
Running UE4 with the proprietary amdgpu-pro driver resolves that, but that’s rather a workaround not a fix.
Whether or not using -opengl4 doesn’t make a difference.
This happens in both 4.13 and 4.14, have not tested other Engine Versions

I’m running Arch Linux, Kernel 4.8.4-1
RX480, amdgpu drivers, mesa 13
Compiled with clang 3.9

Complete log here: