Hi Quanah,
I really appreciate your help. I just started some debugging on the master side, and I found out that the root of my issue was permission. I got the following messages on the masters side:
5418a353 conn=1064 op=6 MOD dn="cn=Lisa Hayes,ou=Quality,dc=example,dc=com"
5418a353 conn=1064 op=6 MOD attr=pwdFailureTime
5418a353 conn=1064 op=6 RESULT tag=103 err=50 text=
tag=103 err=50 ----> This usually means insufficient access. I look over the my HDB access configuration, and realize that my chaining (cn=syncrepluser,ou=security,dc=example,dc=com) user had "write" permissions on userPassword, pwdFailuretime, pwdChangedTime, pwdHistory, pwdAccountLockedTime attributes and that wasn't enough. I changed the "write" permission to "manage" and everything started working.
#-----
# Master
#-----
dn: olcDatabase={1}hdb,cn=config
changetype: modify
replace: olcAccess
olcAccess: {0}to attrs=userPassword,pwdFailuretime,pwdChangedTime,pwdHistory,pwdAccountLockedTime by self write by dn="cn=admin,dc=example,dc=com" write by dn="cn=syncReplUser,ou=Security,dc=example,dc=com" manage by * none
Hope this can help others. Thanks a lot for your help!