Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48
Broken: version: 2.81 (sub 15), branch: master, commit date: 2019-10-18 14:41, hash: rB970d7ed860f1
Short description of error
Cycles just renders the combined pass, but will not create any of the AOVs (they will stay black).
Exact steps for others to reproduce the error
I think this is something that happens at a certain complexity of the scene relative to your gear. Maybe there isn't enough memory to store them, so they are being purged?
I will try to find a way to provoke this behaviour later, but as of right now, I have no clue when exactly this happens, nor what exactly is causing it - the only thing I know is that my projects at a certain point all adobt this behaviour - but when I let them render on a render farm it's fine. Sometimes even just restarting Blender helps