Multisite admin redirects to 404 page after saving changes

Hi there,
I recently noticed an strange behavior in all my multisite sites. It happens in all sites (inside 'sites/' folder or 'env/' folder). The main site works fine.

In the 'Configuration' section or 'Themes' section, after making some change and trying to save it, the page is redirected to 404 page. For some reason after clicking 'Save' the url duplicates the text '/admin/admin' and therefore the url can't be found.

I'm using:
Grav version -> 1.7.27
Plugin admin -> 1.10.27

In my local machine I tried with an older version of the 'admin plugin' and it works fine:
Grav version -> 1.7.20
Plugin admin -> 1.10.20
This way works everything fine

I assume that may be some issue with the admin plugin between version 1.10.20 and 1.10.27

Well, I don't know if anybody else noticed this problem and is general or it is my particular case.
Any help is welcome.
Best,

Hi,
trying to identify the origin of this error I installed a fresh copy of Grav 1.7.29 with admin 1.10.29. I created the setup.php file to transform it into a multisite, according to Grav documentation, I didn't add anything else. Default configuration, default theme, etc.. Everything as it comes with Grav.

And hitting SAVE under the Configuration section the error appears:

The URL duplicates the text 'admin' and appears the 404 page
......../admin/admin/config/system

Replicating the same process with Grav 1.7.20 with admin 1.10.20, everything works fine, Changes are saved as expected and no error is showed.

There is nothing added by my side in both cases. It must be some bug in the code .. ?¿
Nobody else has this problem?

Sounds like a time for a GitHub issue

Thanks @Karmalakas
done https://github.com/getgrav/grav-plugin-admin/issues/2231