There have been about ten different versions of krita that start with the number 5.
The latest formal release is version 5.2.2 and I recommend that you make sure you have that one from the official website: Download | Krita
I strongly suggest that you stop doing File → Save As with saving to .png.
You should always do File → Save and use .kra as the file extension.
Here, in the first post is an example of someone providing a screenshot of the important information about their attempt to make a timelapse recording:
FFmpeg recorder export error
I suggest that you start with a new document of about 512 x 512 canvas size.
Then try to make a short and simple timelapse recording of maybe 10 seconds.
If you want to save that document, do File → Save then give it a suitable name with a .kra file extension.