There are two problems here, both need to be addressed. First, Google does not support refresh-from-client (the one tested here) or one-way-from-client (not in the GUI, could be selected by command line). The error reporting for this needs to be improved. Second, running multiple syncs shouldn't crash the syncevo-dbus-server. Might be a problem of libical (invalid free in icalcomponent_as_ical_string?) but perhaps this can be avoided by using icalcomponent_as_ical_string_r.