Sync errors and possible reasons
From dmfswiki
Below you'll find an explanation of some bug reports and possible reasons.
org.apache.http.client.ClientProtocolException: calendar-query failed
This is probably a server bug. You're probably using ownCloud or an older version of SabreDAV. Try to upgrade your SabreDAV installation (or the SabreDAV part of ownCloud). If you're not using SabreDAV or ownCloud and you get this error send me an email, please!
javax.net.ssl.SSLException: Read error: ssl=0x34b548: I/O error during system call, Connection reset by peer
Probably a connectivity issue. If this happens very often you should check your connectivity or your server.