Very confusing I have to admit. So the filter only appears while being in the car, and with all camera positions? And you don't have the problem with my 2011 or 2013 mod?
If it's tweaker related as Dan suggested, I'd say that it can only be caused by the modified gp4.exes with a damage coefficient higher than 100%, as the other tweaker stuff is the same as in my other mods. Try selecting 100% damage coefficient in the CSM menu, this way your original gp4.exe will be used.
You can also try to deactivate all changes the mod makes in the f1graphics. In the csm.ini, put a semicolon in front of the F1graphics line therefor, like below:
[Misc]
;F1graphics=1,%hres%,%vres%,,,,,,,,,,,,,,,,,,,,,,%hires%,,,,,%32bit%,,,,,,,,%rotate%,,,,,,,%mirrors%,,,,,,,,,,,,,,,,,,,,,,,,,%tvoverlays%,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Apart from that I don't have any more ideas for the moment.
Some mods
F1 1996 | F1 2002 | F1 2007 | F1 2011 | F1 2013 | F1 2015 | F1 2018