When you load an acceptable movie format file into Registax, the first thing you do to it is designate one or more alignment points so it can rip through the file assessing the individual frames for quality (or differences between frames at the point(s) you designate for alignment).
You should then see a message indicating how many frames out of the total are available for processing, and when you click LIMIT you are telling the software to accept that number of frames to process.
If either the file format is bad or your reference point for alignment is inappropropriate, Registax will process only the frame currently loaded (usually the first frame in the sequence).
I suspect you are still seeing a file format problem if not matter what you try you only get a single frame to process.
I use VirtualDub almost exclusively for working with video files to load into Registax. I never see this error, even though I do use some incompatible file formats from time to time, depending on which cameras I am using. VDub does a great job of converting the formats into AVI files -- which Registax prefers.
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