You might have turned on ‘Ignore Event Grouping (ctrl-shift-u) ‘ at the bottom of the screen.
Turn it off and see if that helps.
Jeff
Dell Precission 7810 with 2-Intel Xeon E5-2630, 32GB DDR4, GTX 1080 8GB, Windows 10, Vegas 17, Hitfilm Pro 4 w/Ignite.