That isn't necessarily an indication of corrupt data. It could be a bug. That comes up, for example, if you delete records from a cursor you are iterating over (which should work but doesn't and IMHO is a deep LMDB bug never corrected because it requires a specific data state that you, congratulations, stumbled upon!). But if you hard booted your machine, it might also be corrupted. I'm not keen to try to restore it to find a bug that might not be there.