https://bugs.openldap.org/show_bug.cgi?id=10088
--- Comment #10 from Quanah Gibson-Mount quanah@openldap.org --- If you read issue 8461 as I suggested, it clearly notes that the issue is related to the length of the value being over 512 characters. If you change the cn value to be fewer than 512 characters, it should work.
This comes from the following hard coded limit in LMDB 0.9:
mdb.c:#define MDB_MAXKEYSIZE ((MDB_DEVEL) ? 0 : 511)