Clearly the issue is the white poker chips. If you had used
BLUE, then there would be no problem.
Seriously, though, it's really hard to tell from just that shot as there are so many factors that can go into it causing this issue.
I just fought a similar issue where two sections of track met on a curve. As I was using flex track, the installation wasn't the cleanest/smoothest and it turned out that the inner rail got kinked UP just a touch while the outer rail got kinked DOWN about 1/2 an inch further down the track. Now we're talking maybe 1mm worth of total height difference, but the end results, while not too big an issue for any loco or car with dual axles, would really show themselves when a
three axle truck rolled on. The leading axle was lifted just enough while the rear two stayed "level" with the rising track which lifted the flange up and over the head of the rail. As the train exited the curve and met a turn out, the wheel that was out of place would try to take it's own journey somewhere else derailing the train.
Viewing this section from the top, like in your picture, didn't reveal much. Looking at it from the side was were where I was able to spot the issue.
Check for even (level) track. Especially in a curve, if there is an abrupt (or sometimes even not so abrupt) change in pitch, it can really lead to trouble.
Hope this helps.