Is it "normal" for the band to come off if not perfectly positioned during the draw and to come off one or both arms after release?
It is going to stay in the closet. It was under $4 shipped off Amazon. New bands cost more than the slingshot did.That looks suspiciously like a model I had trouble with a while ago. If it is the same model you should be able to pull the forks apart with your bare hands. The one I had literally snapped in my hands. I hope it is not but best to check because if it is it could come at you under tension and hurt you.
Thank you for sharing a picture. It looks like the bands are really thick and the frame slots are thin, so if the frame was built well, there shouldn't be any slippage. Which means in my opinion, the frame is super weak. I think what's happening is when you stretch the bands, anchor, and release, your frame is bending at the forks causing the slots to open up. That's why there is slippage. Thankfully, it hasn't broken on you yet. I think you should just toss it or use it as your target. Save yourself or someone else from severe pain and/or blindness.Hope this works.
I think bands are around 3/16 diameter.