HELP random shifts in color (gamma)

Hello all,
I'm on Resolve 14.1, grading a project for a friend on my 2017 Imac with 8gb of VRAM.
I'm getting this very annoying issue: sometimes the correction I've applied to a shot seems
to shift for a couple of frames, usually getting darker and crushing blacks.
It will happen randomly, and sometimes disappear after a couple of playbacks,
but sometimes these flashes remain even on export.
It is also hard to spot as they may appear on different places upon export than where they appeared on playback.
It also makes it unnerving to grade as sometimes almost a whole clip is affected and
you don't know where the proper color grade lies...
Anyone has seen this and knows of a fix?
I'm on Sierra (latest dot version) on a late 2017 Imac with an amd GFX card with 8Gb of VRAM but sadly
only 8 Gb of ram for the moment (hadn't expected to get a job at home so soon so haven't had the time to buy more ram).
Any help is appreciated!

What kind of source material are you using? Are you using any color management? How are you judging the image -- is this on an external monitor, or are you looking at the GUI within Resolve? If it's the latter... don't do that. I would verify that the display is calibrated to Rec709 (assuming a delivery in this colorspace) and make sure there isn't any ABL or some other kind of processing going on.