@yisrael-wix
I went through all official troubleshooting. Went incognito, cycled through for possible off-grid elements, cleared cache, flushed DNS, messed with my browser add-ons, even formatted my HD (#not).
Apparently, it was a corrupt (?) textbox. Rather, some corrupt artifacts on top of an otherwise functional textbox. Those artifacts could not be selected/deleted, etc. They were only moving along with the movement of the text-box (that’s why they occupied the space on the top of my page).
How did I find out? Well, I duplicated the erroneous page and started working from there, using the ancient, long-forgotten technique of repetitive Delete & Preview .
Eventually, once the whole element was sent to oblivion, the problem disappeared.
I’m leaving it here for possible future reference or/and reverse engineering.
