exact same problem here on a Mac Pro. with the mini activated editing is horrible. for me it´s unusable. I mostly turn it off.
I have posted this a couple of times in this forum with zero feedback from BM.
This looks like your 2K data has been recorded with the odyssey-recorder. That´s an external device you can attach to the FS700 an record directly into ProRes or DNxHd Codec. The Files from the internal SD-Card look right. Maybe check Clipwrap
all I can say is that the MacPro with Dual AMDs had similar rendering-issues in resolve.
But Blackmagic has fixed this in their latest release. It´s some kind of driver/architecture issue related to that type of graphics card…