Unusual url string being created - how to fix?

[Gemini23]

Can anyone help with this?
Difficult to describe without a url but here goes...

Paginated archives of categories have been duplicated with the full url (although only one '/' in the https:/w)
being added to the main domain url up to the category.

I have deactivated all plugins, changed theme to Wordpress 2017, and checked htaccess - but to no avail...

ie - duplicate of actual page https//:wwwdotdomaindotcom/category/page2
THIS>>>
https//:wwwdotdomaindotcom/category/https/:wwwdotdomaindotcom/category/page2

(and these have been indexed by Google - and there are several hunded of them)
Any suggestions?

[edited by: Gemini23 at 12:25 am (utc) on Feb 13, 2018]

[seoskunk]

Let us know how you get on

[Gemini23]

Okay... checked and also on live site - The Yoast plugin - simply by activating (not adjusting anything else - some settings will need looking at)

THE CANONICAL ON THE 'FALSE' URLS IS TO THE CORRECT (original) URL - So I should expect those 'false urls' to hopefully be de-indexed automatically?

MANY THANKS - It doesn't answer why these urls can even resolve BUT it does make their generation to not be a problem.

THANK YOU!