dino Its same in Safari, as its looks like custom scrollbar used by the page.
Ah, right. It’s the same here.
dino Unable to reproduce this issue on Mojave 10.14.6.
As I pointed out before, this might be a graphics card (Radeon RX580) dependent issue. Some image related apps (Preview, Acorn, …) have also shown this behavior, albeit very rarely and definitely not reproducible as in Orion now. But in these cases, once the issue had started, it occurred with every newly opened image file in this app and could usually be fixed by quitting a different image related app (as if some shared resource had been “full”), whereas in Orion it’s completely independent from other apps and only occurs on specific web pages, but there it always occurs.
Of course, I’m aware that this info is of little help. If it depends on Mojave and an RX580, maybe just leave it at that?
dino Please share a recorded video with screenshot of About window.
Which About window, Orion or macOS?
Unfortunately, I currently can’t launch Orion as it immediately crashes for me (bug 6588).