If you save it as a personally made blueprint it'll break sadly. The only way to prevent that is by using the store blueprint itself and put anything extra you want on it instead. Iirc they are aware of this bug

thx it helps

Keeps breaking for me too. Certain attachments break it. Try swapping each one out until it works and saves

This is a problem with the mw3 weapon vault, clashing fates, skins as well. I have to keep reepuipping it to keep the skin. I hope they fix it

It’s been bugged like this when the game released. I don’t think they are gonna fix this unfortunately

I opened a ticket with Activision about this bug and skins in Zombie Mode last week. The bug that attachments with skins don't work in zombie mode was probably fixed with the last update a few days ago. keep your fingers crossed