The preview plugin is really nice. But it has an issue, when activating the "auto reload" mode - loads the page - you make a change - it closes the preview and loads it again This causes a flicker, as the preview goes black for some milliseconds. An Alternative would be something like only load the updated preview when it is finished, or always wait x milliseconds (easier but depending on document size and processor not that easy). Having the reloaded page fade in using transparency (opposed, current preview fading out, new preview fading in) would make it look awesome and smooth. Currently the flickering makes it pretty unpleasant, even though the live mode is pretty nice.
The preview plugin is not maintained, if you want to have this improved, please submit a merge request, otherwise that will stay the way it is at the moment. https://kate-editor.org/join-us/ I am sorry that does create issues for you, but the only other fix would be to remove it.