Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.70
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-04 22:33, hash: rBab519b91b2c4
Worked: 2.79b release
Short description of error
Enabling MIS in branched PT introduces a lot of noise in every release after 2.79b.
Example picture of the Agent demo:
2.81 Alpha: https://imgur.com/a/uaJ34FV
Exact steps for others to reproduce the error
Download for example "barbershop_interior_cpu.blend" from https://www.blender.org/download/demo-files/, render with a current build in BPT with MIS on and compare it to the much cleaner 2.79b result.