Minecraft version: 1.21.1 NeoForge 21.1.206
Mod version: 5.2.2 (latest)

I made a sandwich with 10 pieces of rotten flesh and the hunger effect was stacked 10 times as well. It should be shown only once since it gives only 30s of hunger instead of 300

It gets worse when you have a lot of rotten flesh in the sandwich

Should be fixed in version 5.2.3.