Added the following property to 'usm.properties' file:
com.openexchange.usm.session.sync.lock.timeout

It allows the configuration of a
wait timeout (before the request is aborted) to
gain exclusive access to a folder in case of
concurrent synchronization requests on the same
folder by the same device.
Its value is a timeout in milliseconds, the default value is 10000 (i.e. 10 seconds).