dquarasr
Registered
DISCLAIMER: I am not an instructor, just a lowly APA SL6.I normally(when missing) undercut when cut left side of ball and overcut when cutting to right.
One should practice more that side of cut which feel unnatural or more difficult.
Sounds as though you are missing the same way; when cut left side and overcut, you are missing slightly cue ball right. When cut right side of ball, and undercut, you are also missing slightly cue ball right. At least that's how I understand how you've described it.
I have found that one cause could be a basic alignment problem. You can experiment with foot position. In my experience, missing consistently one side or the other means my feet were not in optimal position. You can try setting up shots and vary your feet position a few inches left or right of your "normal" positions and see if it helps. It did for me.