I've no idea why 1.5 should be worse than 1.4. Please help me investigate that further. For that, increase the loglevel to 4 in the target-config of the CalDAV sync and run a sync. Was it reported as a normal, two-way sync with no changes on either side? Look at the syncevolution-log.html of the target-config side for that sync session. What is this REPORT which produces the excessive amount of data? It would be useful if I could look at the log leading up to that REPORT. Perhaps you can send it to me at patrick.ohly at gmx.de? Feel free to strip out personal data, although I also of course promise to keep it confidential. It may also be useful to downgrade to 1.4; the archives can be downloaded here: http://downloads.syncevolution.org/syncevolution/archive/ Don't bother if you don't have the time to try that. Perhaps the additional information about 1.5 already gives me enough clues.