Vadim Prozorov wrote:

Did you have dbnosync configured on this backend? Looks like garbage data
got written to the freeDB.

No, DB config section is: # define MDB parameters backendmdb databasemdb maxsize20000000000 envflagswritemap mapasync # end define

Unfortunately, in Linux mapasync is a no-op. It seems then that your DB is quite corrupted.