Black paper lanterns placed in a pattern similar pattern to flint and steel (2x2 grid, with black lanterns in each corner) is considered a valid recipe for crafting more black paper lanterns. This allows duplication in survival. The glitch also lead to a silent game crash (log stops prematurely) while connected to a server. Game version is 1.16.4, attached is a screenshot of crafting recipe.

Thanks for reporting!

Appears I'm neglecting to set the result stack size to 1 from the input ingredient, where this recipe is intended for copying colors of lights. Fix will be soon!

Good catch, I wasn't sure where it was coming from, was definitely curious.

Fixed in Release 4.0.5