Preview + render video flashing grey intermittently

Hi all, I've been wrestling a flashing clip/preview issue the last week, none of the standard fix approaches seem to help.

The problem: With all my Sony Fs5/MXF footage, preview in Premiere flashes grey, as if it's temporarily in slog througout (roughly every 2-3 seconds). This also shows up in the export. 

Tried so far (in vein):

- updating driver (Nvidia quado k5200)

- bring up to date premiere + machine (windows 10)

- installing alternate video card (GTX770)

- My system is and ACPI 64bit, Intel Xeon CPU E5 v3 @ 3.10Ghz

- changed all render, playback, and media settings within premiere i can think of (change renderer, etc.)

effective, but temporary work-a-rounds: 

- converting everything to appleprores

- shooting everything in slog from camera

- editing on home windows system, similar specs (windows 10, K5200 card), no problems there. 

Any ideas would be much appreciated!