I can't see you shoot so I don't know exactly what is going on with your shot, so this is just from past experience from myself and a few others.
Most archers who are freezing off target do it because they are using the sight picture to ignite their release. The way most learn to shoot, this is pretty understandable.
The way to control this is to separate the sight picture and the release. Unfortunately, this is not easy, especially if you've ingrained this into your subconscious.
First step is to develop your shot sequence on a blank bale. Work on a smooth, steady expansion to release. Once you begin expansion, never stop until you've completed your follow through.
Then put up a larget target, at least 24" and begin close, no more than 3 yards. Work on immediate target aquisition. Get your sight picture on the target immediately. Shoot at this distance for 3 days. If you don't freeze on the big target at 3 yards, move back to 5 yards for another 3 days. If you have even one freeze, go back to 3 yards. Don't say "well I won't freeze on the next arrow". Likely you won't but you will have lost the opportunity to train your subconscious to not freeze.
Continue stepping back in 2 yard increments until you get to 30 yards. Then begin gradually reducing the size of the target.
Two keys to this are 1) never stop your release once started. Hesitation on your release will take you back to freezing 2) any time you have even one freeze, stop and go back to the previous distance. If you freeze again, go back to the bale.
This takes a little time and a lot of self discipline, but I've seen it work several time.
Good luck,
Allen