Calendar: scrolling weeks with cmnd/arrows mis-aligns days

In Calendar, i use the cmnd + L/R arrows keys to scroll through weeks in week view. If i do this more than two or three times, however, then the week will become misaligned -- instead of starting on monday, it will become sunday, then after a few more, saturday, and so on.

I believe this only happens with the right arrow, i.e., going into the future.

Using cmnd+T to return to today's date always sets the week to begin on monday again.

Of course my preferences are set: Scroll by: Week; and Week begins on: Monday.

I would happily admit i am simply mis-hitting the keys, except only an arrow, or only cmnd, will do nothing.

Anybody else?

Possible solutions?