can't change ldap_blocked status in web

I hit an issue with this in 8.5.1 - some users became ldap_blocked and I couldn't reset their state. I think there was a temporary connection failure to the ldap server and they could not be authenticated. I wonder if this made them ldap_blocked? Once the connection was restored they could not re-authenticate (possibly due to being blocked) and did not become unblocked. To fix I manually changed their state to "active" in the users db table. My openldap version is

root@vpcd-ldap-1:~# slapd -V
@(#) $OpenLDAP: slapd  (Ubuntu) (May 25 2015 13:12:01) $
	buildd@toyol:/build/buildd/openldap-2.4.31/debian/build/servers/slapd