Probably nothing.

You've held a reaervation on UA.com, at that guaranteed price, and a have a separate reservation through your TA in just Y. they aren’t going to transfer the guaranteed fare to your other ticket, especially since you are upfaring. Not only that, you may have to look at COC, but they could perceive this as holding two reservations on the same flight, a violation of it. In fact, this may make your case worse, as if you’ve taken the last discount fare out of inventory for the farelock, it may not be available, even if you cancel the Farelock.

Id say just drop the farelock, and call UA to upfare. If you don’t like the price, then hang on and see if it comes back. You’re not going to win this game the way you are playing.