http://manual.zorro-project.com/bars.htm

The duration of a 5 minutes bar is 5 minutes. If it's weekend or if the history contains no prices, the bar ends at the next multiple of 5 minutes. I think for most users this is not very surprising. Nothing wrong with StartWeek. If you want a bar to start at a particular minute, use either 1 minutes bars, or a bar offset. For doing something exactly at market open, I would not tamper with bars anyway, but just compare the time.

Your next issue: >>BarPeriod=5 - frameSync(4) almost works.<<

This works not almost, it works not at all. frameSync() is for synchronizing to full hours. frameSync(4) is not a full hour. frameSync(12) would be a full hour. Again the manual is your friend: http://manual.zorro-project.com/frame.htm