https://bugs.openldap.org/show_bug.cgi?id=9626
--- Comment #5 from carlos.velasco@nimastelecom.com ---
The txn->mt_parent pointer is clearly invalid. Most likely some other code overwrote it, probably in ModSecurity. This is extremely unlikely to be an actual LMDB bug.
Ok. I will report it there and reference this case number. Thank you very much for your prompt support.