Include 256 in your loglevel, if you haven't already, and look for the '<date> swizzle slapd[<pid>]: conn=<num> ...' lines it produces. In particular, look for 'conn=<num> op=<num> RESULT' lines _after_ the 'deferring operation' line, where the matched received operation (same conn and op) was _before_ that line. Notice what the operation was, and what the result code was (RESULT ... err=). You'll find the result code descriptions in RFC 4511.
The examples I could find all look like this:
Apr 11 15:06:43 cliff slapd[15355]: conn=1 op=36051 BIND anonymous mech=implicit ssf=0 Apr 11 15:06:43 cliff slapd[15355]: conn=1 op=36051 BIND dn="" method=128 Apr 11 15:06:43 cliff slapd[15355]: connection_input: conn=1 deferring operation: pending operations Apr 11 15:06:43 cliff slapd[15355]: conn=1 op=36051 RESULT tag=97 err=0 text=
I can't find a reference to '97' anywhere in the above mentioned RFC. Is there somewhere else I should look?
-Ben