When using current Winterfall, searching for appointments in Roundcube doesn't work. There is no error in the web frontend, however also "no obvious search attempt" and also no visible failure. I also wasn't able to see an obvious error message in the logs, but last should be verified for sure. To avoid misunderstandings: I'm using the search input box in the upper right corner when being on the calendar "screen" in Roundcube.
As talked with @vanmeeuwen on IRC, he's able to reproduce it, "but it's easier to close a duplicate than it is to go after all unlogged tickets" - thus filed hereby ;-)