Thank you for the additional info.
If there is no traffic at all, then WordPress does not run so nothing can happen. Setting up a manual cron trigger is something that is also discussed in the plugin’s cron job settings screen. And there are multiple articles about it.
However I am not sure this is the cause of your issue. It sounds very suspicious that there was exactly a two hour delay both on start and finish, while your timezone is +2.
This is something that I have tested extensively on my machine, but it is still possible that there is a mismatch between your WordPress timezone setting and the PHP timezone setting. I will investigate and if this is the case I will patch the code to account for this and will inform you again on this thread soon.
In the meantime, if you want, check your server’s PHP settings to see what the timezone is set to. For example, see this article: https://www.inmotionhosting.com/support/website/php/setting-the-timezone-for-php-in-the-phpini-file