[MrFlippant]

Eliminating possible sources of the problem is a good idea, like going back to two lanes as GregK suggested.
If you can't simply unplug the extra lanes, a couple other ideas are to reset the PB to default values, and run some laps with the PC disconnected. I've had some inexplicable issues that went away when I reset the PB to defaults. If you're using SSDC 5.x, although it's pretty solid, there still might be some issues.

 

[MrFlippant]

You can install SSDC v5 and try it out without messing up v4, so no harm in checking it out. It works differently, but I believe everything from the previous version is in v5, plus some other nice things. It's especially good for when you want to run a series of races with friends.

 

[MrFlippant]

Yes, but not because of speed as much as the guide being up out of the slot a little. That's why we like to put the base at the end of a straight before a turn. It's not so that the car is slow, so much as so that the car is slowing down, thereby driving the guide as deep into the slot as the front wheels will allow. This is not so much an issue with magnet cars as magless, but it can still happen.
Oh, and definitely don't put more INOX on. If anything, go around all the tracks with a dry rag to pick up any excess. Also, as Ade pointed out, check all the car's braids and guides by removing the braid plates. If you can SEE the INOX anywhere, there's too much, and it should be wiped up completely.