Hi,
I've found that you're actually using the Brainforge manual shipping plugin and not the standard manual shipping plugin.
If I configure a standard manual shipping plugin and use it, it works fine.
Also, with the way you configured your shipping methods, there is no need to use the Brainforge one, the standard one allows for the same things.
And finally, when I edit a Brainforge shipping method on your website, I don't see the configuration interface specific to it. So I'm wondering if you didn't mess something with it. In any case, we can't debug that plugin as we don't know its code. So either you can ask the developer of the plugin for help, or you can use instead the standard manual shipping plugin which has the same options as you're using but doesn't have that problem.