When changing parameters, the image only updates after you change it again, after which the image will show the image with the previous parameters.
For example, starting with a power 2 Mandelbrot, changing the power to 5 will not update the preview, and changing it to 10 will update the preview to the power 5 Mandelbrot. Changing the power to 15 will update it to a power 10 Mandelbrot.
A similar effect happens when panning/zooming out into areas not shown in the previous change, the panning is somewhat successful but the new areas will appear black. Zooming in will make the image pixelated.
Thankfully, this effect does not show on renders.
I'm using Ubuntu 20.04, and this never happened when I used UF on Windows.