Hi
That looks normal: your home page menu item is set to show precisely the "sh404SEF custom content' category: https://weeblr.com/images/screenshots/MVjLKZI3fdIxayx3ysaYOfq8689s77.png
You have set a custom title for the home page (https://weeblr.com/images/screenshots/BqW4fnyRaObTQOvYr4DvO09qo7F02Y.png), but that's valid only for the home page. If you append something to the url (http://mysite.com/?anythng), then you are on a different page and the custom title is not applied, instead you get the regular title, which is "sh404SEF custom content"
I don't see any problem here, except that I'd strongly advised you to NOT use sh404SEF content category for your home page. That's a reserved category, you should create a separate one and give it the name you whish as your home page title.
Do not change the name of the "sh404SEF custom content" category either, that may break sh404SEF 404 error page handling.
In which case will you have ?rrr added to the URL?
Rgds