If you place sand block, gravel block or any other block with gravity 3 blocks above end portal frame with fences directly underneath the end portal and let the blocks like sand, gravel or dragon egg fall 3 blocks into the portal it will destroy the item instead of teleporting it to the end. Problem is if you let the item fall 6 blocks, item will appear in end and duplicated. Problem is it shouldn't destroy your items.

How to replicate the destruction of item which shouldn't happen in case you accidentally drop something into portal.

How to reproduce

1. Activate end portal frames by filling it with ender eyes. (don't need to jump trough kill ender dragon and come back to overworld portal it wont make difference if it is loaded or not)
2. Put fenced directly under the end portal
3. Place block affected by gravity directly 3 blocks above portal and fence
4. Jump trough portal and discover your items (blocks) are discarded, if you repeat step 3. and put these block 6 block above, your items are duplicated.

Wanted result: keep my items and don't destroy it, just make them go trough the portal.

Link to video of reproducing and showing the bug: https://dropover.cloud/ef50f0