https://bugs.winehq.org/show_bug.cgi?id=54143
--- Comment #13 from David dav75uk@yahoo.co.uk --- I had an idea about this one that seems to be the case.
I run chessbase on wine in 4K mode. If I reduce the display to 2K the arrows are better proportioned. If I resize the board (probably also the same in CBReader) but you can drag the board <-> notation window separator to resize the board, then the arrows scale differently to the rest of the board.
This leaves one of two possibilities:
A bug in the wine version of the draw routine A bug in chessbase (or at least something that wasn't really considered a problem at the time).
My money is on the second one, but I'll try this out on native windows to see if the arrows don't keep proportioned when I scroll the board on a 2K display. Perhaps I can plug it into my monitor and it will display the monitor in 4K mode so I can get a like for like comparison.
Stay tuned.