Steve is right. It is because of how are the tasks and timezones managed, which is not as easy is it may sound, and in no case having problems here is funny to us and neither do we do it on purpose of course.
We are still investigating this matter, but without having feedback as to in which timezones is it happening, if they went through a daylight saving time change, how were tasks supposed to be saved and so on, lets say it is quite hard to blind guess.
If you could share this info with us, it would be much appreciated, but please note that the current latest version: 3.1.2.2 has lots of changes here. Hopefully it solves some of the ones you experienced?
Best regards,
Francisco