Hi the anchor point is bit tricky.
First you have to change the anchor point of the bag to be in top center of the overlay.
First check that the overlay is cut so there is no extra transprarent space around it… In preview you shoud see the white line showing the border of the overlay just next to it… If it looks biger you will eather have to cut out the overlay first or guess the hight of the anchor point.
If the line is close to the beg top the anchor point is I think 0.5 1 in your case.or 1 0.5 lol I myself never remember and have always to try it first.
First you have to change the anchor point before you put the bag on its place. Make the first rotation 0° in 0time so it will not rotate… Just change the anchor point.
Because with changing the anchor point it will look like the bag has moved.
So after you change the anchor point shift the bag to its right position
And rhen just give the rotation command… The anchor point will be the same just change the 0° and time.
If you still have problem give me the overlay ang your script and I will make you the script.