BlackWatchAmbush

Hello everyone. I am new to Rigs of rods and have a few questions regarding some gameplay problems i have seen. the only 2 problems i have had are these. 1. this happens on a very small amount of trucks but if i pick a truck like ghost ryder. i can load it up fine but the wheels are either invisible or just gone. i can see the center piece fine. the truck behaves normally and all. but i cant see them and man its just weird. anyone know how to fix this problem? and number 2. this happens on more trucks than the last problem but some trucks i pick will crash the game /: im still new and im unsure what i need to do to fix these problems. if anyone could help it would be great. Thanks.