Internal Server Error error turns from your server side.Possibly there are some timeout settings/redirects and software cannot Get a big batch of data from your database during specific time period.
As a solution we recommend you to enable " Optimize speed" option ,see screenshot > https://www.screencast.com/t/doosEAZ51cp This option excludes unnecessary database tables to speed up the process.)
You can also try to contact your hosting provider to check the reason for this error from their side and set it up( increase timeout settings on server etc) or please contact our support directly on contact@emagicone.com