Thumbnail Generator - Bizarre behavior

Hi all, I've had the game a few days, and I'm loving it for the most part. I've came across a few bugs in the course of playing, most are minor, but the one I'm about to describe in particular I can't get my head round what is happening! I have done some searching on the forum but haven't found anyone experiencing a similar problem.

I wanted to create a custom thumbnail for a D-series variant which I have reconfigured to resemble the early 90's GMC Syclone, to replace the 'missing preview' placeholder on the vehicle selection menu, using the thumbnail generator app.

Once I click generate thumbnails, the first thing that happens is the resolution of the borderless window changes. It then begins to go through each variant in the series one by one, attempting to take pictures for the thumbnails presumably. Each truck starts stationary, then after a second or two it begins falling, until it crashes into the invisible floor. This happens whether i choose stay on map, or if i don't. The only difference being the background is grey in the case of the latter.
The first time i attempted to take the thumbnails was on Jungle Rock Island, and the vehicle is teleported to atop a large concrete cylinder, some distance beneath the ground. The only thing I could do was open level editor, where i tried to move the vehicles so they weren't subterranean! However even with physics paused, each time the camera changed (i believe in normal play pausing physics stops camera cycling) it would let go of the truck. So with that I alt+f4'd the game. The dodgy pictures that resulted are now the pictures in the vehicle selection menu. I should say at this time i had a dozen or so mods active.

The second time, i first deactivated all mods, and restarted the game. I then entered the industrail site map, opened the thumnail generator app, unchecked stay on map. I then was teleported to a grey detailess scene where again the trucks began to fall until they met their makers, one after the other. I allowed this to run to completion. In addition to the symptons in my JRI photoshoot, a new one manifested. Namely, the window size kept changing throughout the shoot, sometimes encroaching on to my second monitor. Also the vehicles themselves looked very rough, like no anti aliasing was being applied. I suspect the lack of AA may be due to the second monitors graphics being rendered by the integrated graphics chip of the CPU, superceeding the dedicated GPU, because of the second monitor encroachment.

For whatever reason, the pictures from the second shoot were not used. The result is some of the pictures from the first shoot were used. The rest of the vehicles use the stock photos, I imagine because I aborted it part way through that shoot.

In both cases the resolution of the game was changed from my desktop resolution of 1176x664 to 1280x657. Also after the second attempt, it had reverted to a bordered window.
Why is my resolution 1176x664? This was created by the Nvidia settings app, since my old 720p Sony TV over-scans all sides at normal resolution.

My hardware specs:
CPU: Intel Core i3-8350K - 83.5%
GPU: Nvidia RTX 2060-6GB - 107.1% (HDMI monitor #2-GPU)
GPU: Intel UHD Graphics 630 (Desktop Coffee Lake i3) - 9.5% (D-sub monitor #1-Mobo)
SSD: Crucial P1 3D NVMe PCIe M.2 500GB - 163.2%
RAM: Corsair Vengeance LPX DDR4 3000 C15 2x8GB - 75.3%
MBD: Gigabyte B360M H

Thanks in advance for reading my essay! I hope I've provided sufficient information, if not please let me know. I did manage to get a couple of video clips of the falling trucks, however after every re-render the Windows Game Bar stops recording! Ill upload if you think it will be helpful.
Cheers!
Josh