One thing that could cause your problem is if you are jerking the bowstring up on release, rather than pulling straight back, which would cause the opposite reaction at the front end of the bow. This would typically result in low misses, unless you're doing this so consistently that the "low misses" become the new normal.
I typically have the opposite problem. Sometimes I'll give a peculiar little downward jerk on the string on release, which results in a high miss. It took me a long time to realize what I was doing to cause the high misses. Actually, when I was in the middle of a particularly frustrating time of missing and not knowing why, a shooting buddy commented to me that my string hand was coming down on release rather than moving backwards, and that made the light go on.