Please let us know how your troubleshooting progresses.
We had a prewar 30 degree crossing at the TTOS mall layout years ago. It was American Flyer O gauge and the center diamond was a huge piece of phenolic. It was so big in fact that what ever roller was crossing it would be dead for too long of a time, causing the occasional stoppage of the train.
We ended up putting a diamond of sheet metal on top of it connected to the center rail.