Turn hardware accelerated decoding off if you want to add images to a video supported by the hw decoder.
If the saved video still has issues don't use Display acceleration like (VDPAU, ...)
sequential numbered images like 1280x720-001 to 1280x720-060
Don't drag all to the avidemux canvas.
Drag Drop only the 1st image 1280x720-001 the rest will be loaded sequentially
Images must have the same resolution as the video you want to use with!
With a loaded video, the images will be appended at the end of the video.
If you want image sequence 1st, drag drop 1st image, images will be loaded.
Then drag drop the video, video is appended after last image.