Out of the clear blue I started doing the same thing awhile back.
I hold the slingshot in my left hand as I'm right eye dominant, I was shooting just a little to the right of the target.
I didn't know why I started doing this so I started paying close attention to my form and my release.
I hope this makes sense, here's what I found out, for some reason I was leaning my head to the left, so when I would touch my anchor point it was causing me to shoot just right of my target.
I started watching my form, bands lined up straight with the target elbow straight back inline with bands, then tilted my head into the bands so That I was sighting straight down the bands. Then bingo, back on target!
You said you were hitting just left of the target and that's because you hold the slingshot in your right hand, but if you try the same things that I did I think you'll be able to correct your problem.
It's funny how such simple things can make a big difference, I've been shooting for years and don't know how I started doing that but I did. I guess I just got inconsistent with my form.
Hope this helps!
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