Some Metadata Adapter or Data Adapter methods (as the "subscribe" method) should be implemented as fast, nonblocking operations. When you use a Remote Adapter, the Proxy Adapters forces a hardwired timeout of 10 seconds. If a request for the Remote Adapter gets no answer after that timeout, the Proxy Adapter considers the method call as failed (and when the answer eventually comes, the reported warning is issued).
10 seconds seemed to be quite a long time, considering that no significant network delay is expected for communications on the server side.

You could collect more information on which requests get their answers late by extending the Proxy Adapter log. The log configuration for the Proxy Adapter is hosted by the Server configuration file, conf\lightstreamer_log_conf.xml. Please set as DEBUG the priority for the "com.lightstreamer.adapters.remote" logger and let's see what happens.