Hello,
The mod is using the screenshop functionality provided by Factorio, it is not possible to render the screen directly from the/a mod. SO there is not much I can do, except offer some insights on making screenshots.
The screenshot needs to be (re)rendered separately from the game you are playing itself. So for each screenshot the game has to do extra work.
Depending on the zoom factor the screenshot slows down the game, the further zoomed out the more tiles and entities need to be rendered (fetched from memory, sprites being looked up, drawn, etc). So decreasing the area to take screenshots of, will reduce the latency of rendering the screenshot.
Reducing the resolution helps (a bit) as well, since it requires less pixels to be rendered.
If you feel making the screenshots takes too long (new game, small area, etc), I think it would be better to ask on the official Factorio forums and/or file a bug report (after asking around to the experts over there).