Hello ladies and gents. I'm definitely a newb to g gauge, although I've run other scale for decades. Recently, I build a permanent layout board to put under the tree every year as a change from my usual O gauge. Anyway I seem to have great difficulty keeping the Bachmann rolling stock on the track thru the 30degree  crossover.  The track plan is essentially a loop with in a loop, twice around the tree, with older Bachmann brass tube rail and a LGB 30 degree crossover. I didn't have any trouble mating the lgb solid rail to the Bachmann tube stuff and the rail heights are the same. My Bachmann 4-6-0, and my aristocraft fa, have no difficulty, but my Bachmann rolling stock with plastic wheels derails everytime. My aristocraft rolling stock has no trouble. Could this be because of the plastic wheels, flang size of the plastic wheels (IE frog problems)  the cars light weight or something else.   Also would you recommend knuckle couplers or hook and loop types for max reliability?

Sort of scratching my head with this one