Recently had my kdenlive app (flatpack) upgraded to version 19.04 from 18.12 that I used previously. Very happy and excited with new features and design. I had not tried before using keyframes in general and the "Ken Burns"/position and zoom effect specifically. After watching a couple of good tutorials I tried my hand at the process.

Unfortunately I ran immediately into a problem. When adding the first keyframe my project monitor went from displaying the graphic that I had placed on the timeline to a black/blank screen. The project monitor did display the red outline of the graphic's position properly and tracked the movement, but only on top of a black screen. Thinking this might only be a glitch in project monitor, I rendered the project to an mp4. The resulting rendered file only displayed a black screen.

I'm using Linux Mint 19.1 as my OS. Any others experiencing this problem? Here's a link to a video illustrating the process I used...
https://www.youtube.com/watch?v=UUY39HS3tTs

I'll try to reproduce, but in the meantime, maybe you can try with a PNG image instead of a jpeg?

Thanks for the suggestion. Originally I did use a JPG, and then converted that to a PNG and tried it that way too. The result was the same and was what was used in the video to illustrate the issue.

Thanks for taking a look at this and trying to replicate the problem. I'll be looking forward to your findings...

Tried using the appimage instead of the flatpak version, but got the same exact results. Out of curiosity I tried a rotate effect as it is similar and keyframe-able. It worked with out a hitch.

I noticed that there is an opacity parameter in rotate, but not in position and zoom.

OK, I think I figured out the problem, and it appears to be my process/thinking. When setting key frames I had to make sure the zoom and position adjustment was set before hitting the add (+) key frame switch. Even then I had to return to the first key frame and reset it to 100%, x=0, y=0, so that the clip started where it needed to.

Thanks for feedback along the way.