I couldn't figure out why my German Grand Tour events completion did not add up to 100%, even though I had clearly completed all events... until just now. (It happened again with Retro RWD Tour.)

If you run a TT with borrowed upgrades for the FIRST time and then restore to un-borrow, you will find that right after restoring, your TT event is not highlighted gold like it should be (due to the restore process undoing your completion.) However, once it loads your time stored on their server, it then changes to gold. The percentage of completion that you should have received for racing this TT, however, will NEVER be added to the TOTAL percentage completed thus far for that series. In other words, you will never be able to receive the GC for achieving 100% completion.

Notice on Retro that my percentages don't match.

The lesson here, always run a TT for the first time with whatever you have. Get the full credit for it, then borrow to improve your time.

The plot thickens....

I was running a speed attempt in my Hommage R for the team challenge but killed the game when I failed to set a faster speed. When I reloaded, the above screen flashed up. Now I do have credit for getting 75% completion in the Retro RWD Tour. I never got this for the German Grand Tour series, which still sits at 98% even though all tabs are gold. Weird...