I don't think the elbow is too high but your release is forward on the shots you drop your bow arm. I suspect you may be correct in that it is a mental thing. The first shot on the target your release stays level. On the others, it is out and down and there is much more movement in the bow arm.
Not uncommon and one of the key problems to shooting groups. The first shot is free to hit where it wants. The others, you want to hit with the first. You're losing the follow-thru by replacing it with anticipation.