Yes, others have made the same observation as you. Don't know the cause of it. It might be related to recent updates, or perhaps you just need to make sure that your software (operating system and iMovie) are both updated to highest versions. (BTW, the data on your post indicates that you are using Windows, but I assume that you mean a Mac.) .
A workaround is to do a File/Export __ Photos from the Photos app itself, exporting (in your case) the edited video to your desktop. Then drag the video into the timeline of an iMovie project.
You can also try importing into a new project and/or deleting preferences. To delete preferences, 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 library. Reopen your old library to get back to your projects. Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.
If no success, you might consider calling Apple Support. The techs there have the capability of remotely accessing your computer that we cannot do here. To contact apple support click on the Get Support item in the upper right hand corner of this forum’s screen. Navigate to a place where you can enter your phone number.
-- Rich