Root-relative paths being rewritten on ‘Edit Page’ [closed]

WordPress is strongly opinionated about using absolute URLs. It’s not right or wrong, just the way it is. One of the reasons for their decision is exactly the unholy complexity of migrating relative URLs, which can be very hard to adjust when moving levels is involved.

If existing WP install is using relative URLs, then someone had to go extra mile to make that adjustment. It is hard to guess what they have done and how.

For a long term solution practical recommendation is too comply with WP native approach and normalize to using absolute URLs.