I bought a rockpi4a, rockpi 4a/4b heatsink and rockpi 4.x M.2 Extension board v1.4.
When assembling these three pieces, it showed that the screws nuts from the extension board v1.4 that are intended to be used as distance washers between the rockpi4 and the heatsink where too thick by at least 1 mm.
I tested this by applying a thin layer of the heatsink paste to the SOC, assembling, disassembling and then checking if any the heatsink paste had made it to the heatsink. Which it did not. Then i started to file/rasp off from those four washers, repeating the process a few times, until finally i saw the heatsink paste made good contact with the heatsink on the complete SOC.
Please provide thinner washers with the M.2 extension board that do fit so that the SOC has good contact with the heatsink.