I transferred my save to another computer and found that the mechanical safe could not be opened… I’m sure I started the game with the original user name.
Did you transfer it from Singleplayer to Multiplayer? That might be the Issue.
As for how to get it open, the worst case would be to use an explosive to open it, though I am not sure how that affects Inventory Item drops, lemme check.
Edit: okay Explosions definitely dont destroy part of the Inventory. They will drop 100% of their Inventory when exploded. (this is ofcourse unrelated to your Issue of ownership, which I am still looking into)
I’m sure I’m in singleplayer, but I use a different starter.
Could it be that you are not logged into MC? That might be the Issue there.
I will add a Config for this called “ResetPlayerOwnershipOfGT6Blocks” which should work for any SinglePlayer instance.