imovie-after setting durations of clips, it changes back to original

I'm just trying to cover the bases.

When you say that it starts out as "0.2 s of 0.2s" that description would apply to a video clip, not a still image. The duration of a still image would show as "0.2s)" not "0.2s of 0.2s". So, again to cover the bases,

do you perhaps have a fragment of a video clip in your project?

If not, try deleting preferences and see if that solves it. Open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new empty library. Reopen your old library to get back to your projects. (To reopen your old library close iMovie and go to your Movie folder or wherever you have your old iMovie library stored. Double click on the library’s icon.  iMovie will open in that library.) Possibly you may need to reboot to set the changes.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

Also, you can try putting your media into a newly created project and see if the problem is resolved there. Sometimes glitches are confined to just one project and does not iexist in others.

As for your comments about the iMovie app in general, this is a consumer forum. None of us here have any input into Apples software decisions or designs. To communicate directly with Apple, click on this linK:

Feedback - iMovie - Apple

-- Rich

Did you remember to press the return key to set your duration changes?

.. Rich