After the note shift you see (within the MIDI RAW view) that the first note has now an item offset stays at +xx > 0, no matter if the item begin at 0 or not or you move the note to the beginning of the item again -after shift.
example pic after note shift and moving the note & left edge of the item to pos 2.1.00 again
The event content has now an permanent item offset at +49
1.
30.01.15
EDIT:
Fixed with 5.15 pre7 !!! offset +0
Thank you.