What are the pixel dimensions of the photos that you are using in that Time Lapse Timeline? 2886x2164
Were any resized to 1920 x 1080 prior to import? no resize - I use the zoom effect.
Are the GoPro stills jpegs? yes - but have been lens corrected i Camera Raw and saved again with new names
What is the total duration of the Timeline Time Lapse video? before cut - 19 minutes 28746 files - after cut 1,54 minutes
If you select File Menu/Project Archiver/Copy what are you setting for the Copied Folder that will be generated? a folder on the HD
and
What do you see in the Project Archiver dialog for the following when you select Copy option
Disk space Available 1,1 TB
Orginal Project Size 19.8 gb
New Saved Project Size 19.8 GB
I have just made a succesfull project archiving of an other video made from various movieclips.
But it didn´t change anything regarding the time lap