Hello,
I played around with the Light Campaign a bit and found an issue in the early years with unlocking automatic transmission early through R&D:
I started researching drivetrain stuff from 1946 on and developed a prototype car within 26 months. Then I wanted to create a facelift to properly hit the premium market with the new automatic transmission (normal unlock date 1950). I can select the automatic transmission, but the 2 gears option is not yet available. Instead I get an endlessly spinning Automation logo:
I finally get access to the 2 gear option in January 1949 (my drivetrain tech evel is at 1.94 then, tech date at 12/1950) which is too late for my customers. 
So somehow the ratio unlock date might be different from the actual gearbox unlock date.
Here’s the campaign save file in case you need it for investigations:
BAM_Manual.zip (520.9 KB)
Cheers,
Martin
We’re looking into it, thanks for the savegame, that’ll help reproducing it quickly.