Soo… much going on in there
You initial problem looks like it stems from the main timeline being relative.
Uncheck it from being relative and it appears to work ok.
A second thing I notice is you have some key down event action to continue the timeline. Not sure why but they get called when I hold down or release the command key for example.
There maybe a good reason for this but I would have thought you only need them on the timeline action so the scroll will still trigger them but so will the buttons…