I am having issues with 2 lots of clips and I have figured out that what they have in common is that they were previously rendered in MacOS, one from iMovie and the other from Lightworks. First I tried importing them into a project in Kdenlive version 20.04.0 and after importing I could not drag them into the timeline. Then I set up my project in version 17.12.3 and although they play ok in my Project view. after rendering they come up black with audio only. All other clips are fine. Is anyone able to advise on this issue? Many thanks.

you have to provide at least a small clip made with these 2 apps.. just 2-5 seconds clips to make developers able to reproduce the issue.