slapd[4434]: conn=115331 op=0 do_extended: protocol version (2) too low(...) Where should I start looking?
At ITS#7107, which also had slapd thinking an LDAPv3 connection is v2. So, try the latest OPENLDAP_REL_ENG_2_4 from Git where it is fixed, or just commit 66943cad082eb0cbe19259b05a578bb318e511ad. -- Hallvard