One Identity error connecting to LDAP gateway

When attempting to connect to the LDAP gateway from One Identity's LDAP connector, One Identity is throwing an error regarding it:

2018-07-13 00:50:51.1156 FATAL UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Error parsing condition.
syntax error!
Value "" was found, but one of the following values expected.

Unfortunately it's not a very helpful error.

The full logs of what One Identity is doing are as follows:

2018-07-13 00:50:46.7972 TRACE UFY-1IM-WEB01\UFYAdmin (SqlLog ) : -- Connection 1 switched from Working to Available 
2018-07-13 00:50:50.8968 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Simple LdapSearch BaseDN: '', SearchScope: 'Base', Filter: '(objectclass=*)', RequestAttributes: 'subschemaSubentry' 
2018-07-13 00:50:50.9594 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : LdapSearchResult code: 'Success' entries: '1' 
2018-07-13 00:50:50.9594 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Schema DN is 'cn=schema' 
2018-07-13 00:50:50.9594 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Simple LdapSearch BaseDN: 'cn=schema', SearchScope: 'Base', Filter: '(objectclass=*)', RequestAttributes: 'ldapSyntaxes,attributeTypes,matchingRules,matchingRuleUse,objectClasses' 
2018-07-13 00:50:51.0062 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Got 16 elements of type 'ldapsyntaxes' 
2018-07-13 00:50:51.0843 TRACE UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Got 34 elements of type 'matchingrules' 
2018-07-13 00:50:51.1156 FATAL UFY-1IM-WEB01\UFYAdmin (SystemConnector ) : Error parsing condition.
syntax error!
Value "" was found, but one of the following values expected.

In the logs, we can see that it's requesting certain attributes from Broker:

'ldapSyntaxes,attributeTypes,matchingRules,matchingRuleUse,objectClasses'

And this can also be seen from a wireshark trace:

But when Broker responds, we're only sending back 4 attributes:

I'm unsure if that's the cause of the issue, as One Identity doesn't provide any more information regarding the connection. But it's the only discrepancy that I can see.

The pcap file is also attached for reference.

Output.pcap