Its always more realistic ti buy seperate crossing gate and grade crossing flashers. Bachmann's product is designed to be a cheap accessory to the kind of layout a kid would have on his floor. If you want to make a real grade crossing, go buy kits and such. they have actual working flashers, and gates, that work more realisticly once you put in detection devices. The bachmann one probably depresseses (aka runs over) a "button" that sits in the middle of the track, that moves some gears ( no motors in there whatsoever). the wheel flanges get caught on this, and that causes lots of trouble.
In the end, its much more realistic, and better operations wise to invest in a kit like those from NJ international, and buy whatever detection unit you want for it. That way the lights will flash, the gate will lower as the train approaches, not when it hits the crossing, and most importantly, you can position the crossbucks and gate anywhere you like, adding flexibility.