Can't figuring out what's wrong. Please help.

[HeroToXero]

So on our robot we're using the van door motors to lower our bridge and for our launching mechanism. The problem is that when we throw the bridge in reverse it kind of stutters/is really weak/doesn't work at full power. We've switched the motors out and found that it wasn't the van door motor, so something must be happening to the information from the programming to the jaguars. If anyone else has had this problem before please help. Thanks!