It's been a couple of updates since I've had this weirdest glitch.
On imported RAW images, when the preview resolution is set to anything less than "Full", the layer's gamma suddenly gets waaaaay off. But this only happens if "Linearize Working Space" is checked in Project Settings.
I can correct the layer's gamma manually when needed, but it's still a major workaround to get the preview working properly.
Unfortunately I can't seem to find on which version thig bug appeared, since I do not have acces to anything prior to 17.7 and the glitch is still present there.
I am currently using AE 18.1 on windows 10, Camera Raw is up to date, the RAW images format is .RAF and this bug appears whether GPU acceleration is on or off.