Solved

Research

Are we not allowed to have nothing ticked?

I had nothing ticked before the race and after the race I found this:

It appears that something has to be researched. Luckily it didn't untick the other areas as that would have resulted in something around 40% research and possibly thrown off your testing for the last race.

You can save to only research something you won't make gains in.
It's a method Jack considered, I bet :)

OK, so the problem here was that James ticked nothing, which isn't possible, and thus the system ticked everything? If he'd ticked any of the stats he reached cap the game would have accepted that choice and it would result in no research? Good to know.

Brazil was the last test at the end of Abu Dhabi car and engine both reset to full strength automatically, unless the end-code has gotten changed.

I just forgot about the automatic and free repairs at seasons end.