KnowledgeTree Community Edition

We are developing a simple plugin for a client with KT comercial 3.7

When retrieving the metadata with the sample code below:
$ktapi = new KTAPI();
$session = $ktapi->start_system_session();
$documentK = $ktapi->get_document_by_id($document->iId);
$metadata = $documentK->get_metadata();

I have access to all metadata of document except Conditional metada, after if I execute a simple update to metadata with no changes:
 $documentK->update_metadata($metadata);

All the Conditional metadata are lost.

How can we resolve this issue ? We must have access to all metadata and have the possibility to change some info, save and don´t lost any metadata.

Regards,
Vitor Simoes