I've noticed that if you stand next to the train where the wonderfizz there are 3 bugs;
1.if you look down through the planks at certain angles they bug out causing the ground below to dissapear (noticed on round 31 so it might be due to my particles dissapearing)
2.if you stand with your back against the train your bullets hit it causing some weapons to not damage the zombies
3.the special zombie can shoot through the train if your close enough