portal problems

i have a train that goes into a portal then 5 mins later it comes out of a portal with only the first car of the train, and they go in the portal set to return to another portal. Example

Portal a goes to portal b

Train goes in portal a but dosent return out of portal b.

One Wiki page you might look at is http://online.ts2009.com/mediaWiki/index.php/How_to_Use_Portals.

In particular check its warning about using portals while the TRS19 Compatibility Mode is set to Maximise Performance. This is a setting designed for developers only. For normal TRS19 use this should be set to Maximise Compatibilty