How to extract all images from avi when FrameRate is not Integer

Solution:

The error described below has nothing to do with mathematica (as you veryfied it) but with Quicktime. Mathematica used the Quicktime decoder which produced the mistake. Quicktime extracts image 20 as beeing the same as image 19.

After deinstalling Quicktime mathematica extracts the images correctly.

Thanks to everybody, especially for the hint of Theo Tiger who wrote: Can it be a codec issue?

See also these links:

https://github.com/SimonWoods/MathMF/

https://github.com/kmisiunas/ffmpeg-mathematica

"Mathematica's (v9 or v10) default methods uses QuickTime that produces artifact in uncompressed videos or duplicated frames."