Bluetooth arrow-keyes jumps to the bottom of a webpage

I am (still) experiencing an issue when using a bluetooth keyboard - more specifically the arrow keyes.

For example, when I am writing a post on a forum - like right now - and decide to use the arrow keyes to move the text-pointer/indicator/selector, it works just fine.

But if I tap anywhere outside the textfield to, for example scroll the page, before going back to writing in the textfield, it then causes the page to immediatly jump right down to the bottom when I use the arrow keyes - as if they where also locked into scrolling/moving the webpage.

Do we know why this happens?

(Oh and if you are wondering about the weird formatting; it is a result of copy-pasting the text from my previous question here in the community)