You will get a message like "LDAP sizelimit exceeded, not all entries are shown." when you hit the LDAP search limit.
OpenLDAP: See the OpenLDAP settings to fix this.
389 server: set nsslapd-sizelimit in cn=config (may also be set per user)
other LDAP servers: please see your server documentation
Invalid syntax errors:
If you get any strange errors like "Invalid syntax" or "Invalid DN syntax" please check if your LDAP schema matches LAM's requirements.
This can be done by running "Tools" -> "Tests" -> "Schema test" inside LAM.
If there are any object classes or attributes missing you will get a notice. See LDAP schema files for a list of used schemas. You may also want to deactive unused modules in your LAM server profile (tab "Modules").
If your schema is correct you can turn on LDAP logging to get more detailed error messages from your LDAP server.
slapd.conf: In /etc/ldap/slapd.conf turn logging on with the line "loglevel 256".
slapd.d: In /etc/ldap/slapd.d/cn=config.ldif please change the attribute "olcLogLevel" to "Stats". Please add a line "olcLogLevel: Stats" if the attribute is missing.
After changing the configuration please restart OpenLDAP. It usually uses /var/log/syslog for log output.
Sometimes it can help to enable PHP logging inside LAM. You can do this in the logging area of LAM's main configuration. Set the logging option to "all" and check if there are any messages printed in your browser window. Please note that not every notice message is an error but it may help to find the problem.