I was only able to have this happen once, but I was just playing like normal and opened a shulker box and quickly closed out of it when I noticed it caused me to take damage. I did it over and over again, and eventually I died of fall damage from it. I tried re-creating it, but was unable to. I guess my character got stuck in the shulker box somehow, but I'm not sure how. I recorded a video of it and attached it here. Since I wasn't able to re-create this, I'm not sure what versions it affects, but I was playing in 1.15.2.