There's an upstream bugreport for vega64 which seems to be the same bug:
https://bugzilla.kernel.org/show_bug.cgi?id=201067
- Bug#916797: linux-image-4.19.0-1-amd64-unsigned: 4.19 + amdgpu... Axel R.
- Bug#916797: linux-image-4.19.0-1-amd64-unsigned: 4.19 + a... Axel Regnat
- Bug#916797: linux-image-4.19.0-1-amd64-unsigned: 4.19 + a... Axel Regnat