diffusae:
I nevertheless get the "clock jumped" warning once a day:
"Jan 21 18:34:53.000 [warn] Your system clock just jumped 398 seconds forward; assuming established circuits no longer work."
3-6 minutes difference is quite much. I also have a ntp daemon running and don't know why this happens. The clock is synced?
This may not be related to this issue. "clock jump" may not be a clock jump actually. E.g. one can just "pause" all TCP connections for some time (e.g. on a firewall/DPI/traffic shaper) and then resume them. In such case tor will regard this sleep/resume in the main loop as a "clock jump" thus breaking all circuits. This is because it produces ticks each second in the same thread as the main loop (which is blocking awaiting for data on a socket). There should be a ticket for this, maybe someone can arrange it.
-- Ivan Markin