The numbering of the images has to have one common name, then the computer sorts by number, and it can be thrown off id the number part odf each name doesn’t have the same number of digit places. If the last frame of a sequence has three digits, for example “testframe100.jpg”, the first frame has to be saved with zeros as placeholders so it reads as “testframe001.jpg.” Then the computer (any computer) will keep things properly organized.
When I import jpeg or targa sequences, I create a separate bin for them, and pre-set the default duration for imported graphics to one frame. Grabbing a folder of the stills from whatever application exported them, I drag and drop this into the new bin and, assuming the naming convention I mentioned is correct, all is assembled correctly.
From there I can do a “select all” and drag the entire sequence to the timeline. Generally, at thast pooint after I see how I like it, I’ll render out that part fo the timeline as a self-contained MOV file and import it back over the stills, so ti acts just like any other clip. It is not the only way to do this job, nor is it necessarily the best way; but it works for me.