I bought a few upgrades for my NSX and then, I guess I had 5 racing points and I tried to buy the front mounted intercooler (6 racing points). Then I saw the "You have -1 racing points." I went did a few other stuff like crimes and stuff alike; Then I came back to the upgrades to share that line. And I realised I have 5 racing points AND the front mounted intercooler was installed.
I checked your logs and can't find that buy - perhaps there was some sort of confusion? Can you please try to replicate this on any other detail, that you don't have atm?
I didn't take a screenshot. I'm 100% sure I haven't misread something I tried to buy the 6 point upgrade when it actually bought it, I scrolled up and realized I had negative RPs remaining. Then I go around a bit and then return to copy that line when I see I have 5 racing points and the upgrade isn't uninstalled. I've been using it ever since. Didn't occur second time. I tried buying things I couldn't afford.