From what i've seen in my tests the "Perfect loop" setting doesn't seem to be doing what I would expect it to do.  I believe, it should be making an additional interpolation between the last and the first frame in the end of the video.  However this mode deletes the last frame and just interpolates the panultimate frame to the last one. Is it how it's supposed to be working??

I can easily bypass the issue by duplicating the 1st frame in the end of the sequence, but it's just very counterintuitive to me.