sorry if posted already, I looked some and didn't find anything similar..
When making a sword, I had to set the damage in Mcreator to 4 to get it to be at 6 in game..
Issue comments
When possible, attach your MCreator workspace (or even better a minimal example workspace required to reproduce the bug), game crash logs (full logs, do not crop them, in text format, not screenshots of logs) from the Console tab or terminal and steps to reproduce the bug in your workspace.
Please correct your ticket to follow the rules:
You did not even specify Minecraft version.