I made a post about this the other day, and it got removed for seemingly no reason. And it's concerning, because I've checked the dev team's Trello Board and this doesn't seem to be listed as a known issue in Zombies.
/u/TreyarchCM, I can confirm that since the latest patch, applying blueprints in all Zombies modes seems to cause a myriad of strange loadout corrupting glitches, including duplicating weapons into non-existent weapon slots, stripping upgrades or completely overwriting other weapons, the duplicated weapons cannot be dropped under any circumstance, any attempt to upgrade them will eat points and salvage with no yield, and will cause guns picked up from the weapon box to be lost to the void.