Thanks to Bushcat for these tips. If you still have trouble, send me a PM or mail.

Make sure all modules are at ground level,put troops vehicles etc within 200 Metres.
Dont put the different modules close together.
Put your troops and define faction module away from the core module.
Also put down at least 1 vehicle of each type for faction.You can turn the chance of spawning off in the modules. If you don't then it may spawn a default Nato type.
I believe this is what happened to me.I did not place a ground attack plane even though the russian faction has one,so it spawned a Wipeout.