If you want to make a custom item out of someone else's custom item, clone it and then save it. But don't be a c*nt and upload it as if you made it yourself, if you're going to upload it give credit to the creator.
A lot of people have been having issues with Custom Items, Roleplays, Levels, and Contracts. To fix the problem go to the search bar. There will be a puzzle piece with a red "X" on it. Click on it, and press "Run all plugins this time". Now everything should work fine.
You can refresh. Crashing is 100% voluntary so it's intentionally convoluted.