Just logged in on my blacksmith and tried to open a few Ghost Iron lockboxes and when I right-click on my stack of Ghostly Skeleton keys it immediately starts unlocking even without me selecting a lockbox. It goes through the whole cast and then I get an Invalid Target error.
Disabled all addons
Logged out and back in
Trying to log back in after exiting WOW entirely but no luck yet
Note that this account does not have the Dragonflight xpac
I just started having this same problem today after it was working with the same keys I made just a few weeks ago. Sent a lockbox from an alt to my blacksmith and now getting this issue with it (Eternium Lockbox, Golden Skeleton Key). Given it’s been over a year since you posted this and it was working afterwards, either it’s just intermittent, or the latest game update broke something. Since this also doesn’t seem to be widely reported, definitely an issue on an individual basis.