try increasing the time that it spends in the station. on a coaster that I recently made, the second train kept getting stopped at the top of the lift. I increased the time in the station and it kept doing it. so I kept increasing it until everything ran smoothly. one train doesn't leave the station until the other is about to enter the final brake run, but there's almost never stackage, there's never a train stopped on the lift, and its very realistic.
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-Bob (formerly Coaster Jedi)
Knott's Berry Farm Cuba ~South Park
"Your proctologist called, he found your head!" ~Jerry "The King" Lawler