Major Scaling issue in output in R14 and 14.1

I am facing a major scaling issue while outputting.

My project (all r3d files) is set at 2048x858 and the grading is over. Now we need to output the timeline to Prores XQ so that we can re-lay the output on the timeline to remove the grains.

At this stage, we are changing the timeline setting to 2048x1080 for rendering out the XQ file, just to keep some headroom in case we need to adjust frames later. After rendering out and laying the XQ file on the timeline a strange thing happens. Once we change the timeline setting back to 2048x858 some portion of the timeline remains fine, while some other portion gets zoomed in. A strange thing, but this is happening. And which portion will get zoomed in and which will not, is not consistent. I have tried out rendering out several times and this zooming out thing happens randomly and at at different places every time. Upgraded to 14.1 and the problem remains.

If I render out in 2048x858, there's no problem in scaling.

This problem has never happened to me till 12.5. So, is this some kind of a bug in R14 or am I missing ticking some new box in R14?

Please help, as I am stuck.

My machine:
Mac Pro 5.1, 12 Core
SSD boot drive
12 TB Raid zero
1 TB SSD for Resolve Cache
Titan X
Decklink Mini Monitor (I have tried both HD setting as well as match timeline setting without any difference in result)
Mac OS Sierra