the switchback bags being quick release are not attached the same way as the touring bags.
the Dyna uses 3 pins and a rotating cam locking mech on the rear upper pin, if this is not spot on it doesn't lock but you think it has then when it works loose bye bye bag
1st pic shows the 3 pins on the bike - yes the lower one is on the fender
2nd pic you can see the cam lock with the diagram
3rd is the component parts of the mounting system - totally different to the baggers