Joost, have you installed the 4gb patch to your cfs3.exe? It probably isn't it, but it's worth a shot. I was trying to think what might be different by default with WOTR/WOFF where this problem never surfaced over there, and this was what came to mind.
View attachment 72090
... Anyway I made some (rather minor) changes that may fix the problem, but I need you to test this. ...
Here is a new version (again): https://1drv.ms/u/s!AvmtwF9vPtwVgcNAHdHQnWR1TVz6uw?e=WmsYlK
This time I've used Win7 to debug and immediately found a bug with in-cockpit reflections code which is very likely the culprit.
Frosty, please ignore the yesterday's (Nov 07) build and try this one
==========
Microsoft Combat Flight Simulator 3
build 030203.01 run at Mon Nov 25 17:27:35 2019
==========
CFS3: EnableAsserts: true
CFS3: ExitOnAssert: false
CFS3: SingleAssert: false
CFS3 ERROR [<graphics> cdirect3d(430)]: There is not enough free video memory to run. To correct this problem, reduce your desktop resolution or change the bit depth from 32 to 16.