I don't have time to write a long issue, but I'll try to make it clear with the minimum words possible.

Many blocks, such as he shell, have been added to safe_nbt.json (see here), which causes them to retain all NBT data when using the schematicannon. In the mod settings, he shell can only hold a few types of fuzes, but using NBTExplorer allows players to forcefully change the carried items to anything (e.g., a shulker box with OP items), as shown in this schematic.

Referencing the Create code BlockHelper.java:238, if an item is in the safe_nbt.json, it will be printed with full NBT data; otherwise, if the block has a writeSafe method, only the data in writeSafe will be retained. Blocks like he shell and other blocks added in Create Big Cannons have the potential to be exploited by players to duplicate items (the example schematic I provided was intercepted on my server). Please promptly add writeSafe methods to these blocks or classify them as FRAMEDBLOCKS, and remove them from safe_nbt.json.