To: davecooper
Dear user,
To avoid the problem please try to change the quality of the video preview both on the timeline and on medialibrary by clicking on the Edit button on the top toolbar - choose Settings - General tab - Preview section: choose "Low (Fastest)" in "Quality" drop down box to get the best processing speed.
Please also uncheck the option "Use original format in media library" - you will get good processsing speed.
Inform about the result please.
Kind regards