Probably earlier versions like 22, 21, 20,19.5,18.5

Record something in higher frame than export.

For example - 120 fps, 30 second recorded.

Use the time remapping.  So down to 20%.

Expand the time line of the video to include all 2 minutes 40 seconds.

Go to Export.

Change export settings to 24 fps. 

Video is slow motion.  All the frames are there.  I have a file of 1.8GB.

Export again - video is slow motion - but choppy as anything - frames are dropped/ignored. Export file is 1.0GB.

Note if you do editing like color correction, a new blue effect, stabilization on the first time, you have greatly increased your chances of having a choppy video on export with missing frames.

I don't think I'm doing anything wrong.  I even tried changing the export window back to 60fps and then back to 24fps, didn't reset anything to make it work.

I've been fighting this for years.   I can't be the only one, multiple machines, desktop, laptops, multiple versions.