With tameable treasure slimes, putting an item that is rendered as a full block when held (i.e. emerald block or cobblestone) renders the block above the slime instead of inside. Items with item sprites (i.e. emerald item or potions) are fine.

Thanks for reporting. Will fix.

Thank you for the fun mod :D

:) Should be fixed for 1.1.5c-beta which is processing for upload right now.