Hi Eric: This is a very common problem that usually results from people riding horses with "contact". It's important that horses learn to seek guidance from your rein cues, however, they need to learn to follow your seat and leg cues more than anything.
If you or your trainer are in a hurry to teach collection; you may be creating more problems than progress. Collection is an issue of impulsion. Riding with contact serves to teach horses to be heavy on their forehand, instead of using their hindquarters properly, and with impulsion. Teaching a horse to round their backs and break at the poll is only a small part of the process of collection, that is best reserved for later in the horse's education.
Initially, you should work on creating a foundation of simple whoa, go, turns, and transitions using nothing but your seat and legs. "Ride the buckle"- so to speak - with your hands. Developing your horse's ability to follow a feel, no matter how subtle, will create a horse that is very easy to ride and extremely responsive. It also places a great deal of responsibility back on the rider to have his/her skill, timing and feel at a point of excellence so that he/she can communicate to the horse with a level of refinement that is well beyond the achievements of most horse & rider partnerships.
Take care & best wishes to you. Let me know if I can clarify anything for you.