The owner of the van that was stolen and used in the armored truck heist starts listing off the things he likes about the new van he got from the insurance money, one of them is him saying that his new van has a payload capacity of over 3,000 pounds. Yet the van he has is a Ford Econoline E-150, the 150 is only a half-ton chassis. While it can haul more weight than that, recommended maximum load for a E-150 is 1,494 pounds, doing so on a regular basis would cause a lot of extra wear on the frame, wheels, axle and brakes, which is something a contractor like him would know. If he is regularly hauling more than 3,000 pounds he would need at least a E-250 which has a recommended maximum load of 3,524 pounds.
Only two security guards were shown in the armored truck, but they always have a minimum of three guards. Two of them escort the money as it's going to and from the truck and the third stays in the driver seat with the engine running. Plus the guard that was watching the street did not follow procedure, he saw three men approaching who were wearing masks and carrying guns, yet he didn't raise his gun and warn them off or get his partner's attention and let him know there were suspicious persons in the area. This could be explained if this was an inside job and he were the inside man, but if it he violated procedure big time.