URL is changed to relative in manual entry

When setting a link with a manual entry for a caption, the absolute URL for the site’s URL is changed to a relative one. We run a shop in a subdomain which is it’s own WordPress installation, e.g.: https://domain.com/ourshop. When we try to enter an absolute URL to a product in the small editor that is provided at “manual entry” for the caption, e.g. https://domain.com/ourshop/shop/productwhatever, the editor turns it to ../shop/productwhatever.

We have a development installation which is basically the same installation without live data. When we enter the the absolute URL there it works fine.

Are there any settings to avoid making URLs relative? Can we adjust the behaviour?