hey there. Could you provide more details on the softlock? Getting the core is intended. After that you leave the basement to fight Nex at the mansion entrance. If you equipped the shackles again then you need to go back the way you came and buy the item at the garden shop to remove them again.
when i loaded the save file again today, it somehow got solved and now works fine. What happened is that, once i got the core, the way out of the basement wasn't unlocked for some reason, i couldn't get out even *without* the shackles equipped. Guess closing and opening the game again solved the issue and i could finish the content. Maybe it was a my-pc thing? Idk. Anyways, this was a really nice update! Loved the content