I have tested:    CinGG-20211231-x86_64.AppImage    with all of the Video Transitions (only 2 of Shape Wipe).  Now that I did it correctly, they all work.   I forgot that each side of the clip has to be of some size --  delete a sizable section from within the video" is stated in the manual but obviously applies to size of clips also.  So check the sizes of each clip to be sure there is enough material to perform the transition.  I have not been able to prove that shortening the length of the transition makes any difference in its capability of working or not.  If you have a concrete example that is not working, that you think should, explain how to generate that problem.

To show how video transitions might not work for certain ones, make a single cut in a video (x), drag the Dissolve or IrisSquare transition there and play and you will see it not work.  However, the Zoom transition does work.