Does all those pages have ?cat=-1 in the end? this means category with Id 1 is being filtered for that specific page. It is not being done by the theme.
Are you using any category filter/permalink plugins? If you are then try asking their respective support channels.
Also, please remove your redirect and check the following
1) mywebsite.com/page/221/ if this opens a specific page on your site then
2) mywebsite.com/page/221/?cat=-1 do not redirect this page to your home page, redirect it to the page that open in 1). In the current state you might be redirecting all your pages to your home page.