Steps to reproduce:
In Discourse you can scroll between posts using J and K (like good old Google Reader, or emacs!). Here I scroll from the top of a thread to the bottom in Firefox:

You can see that the scrolling both of the content in the window and the scroll bar of the browser tab itself moves smoothly.
Here’s the same thing in Orion:

(I also scroll back up again with K after scrolling to the bottom in Orion.)
As you can see, it’s juddery and jumps up and down unexpectedly. It’s quite disconcerting.
I also tried this in Safari (Version 15.5 (17613.2.7.1.8)) and the behaviour there is as expected (i.e. the same as Firefox).
Expected behavior:
The scrolling should be smooth, with both the content and the browser's scroll bar moving in sync and in the desired direction only.
Orion, OS version; hardware type:
I’m running macOS 12.4 on a 2021 MacBook Pro 14” with M1 Pro CPU. I’m using Orion Version 0.99.115-beta (WebKit 614.1.12).
(I was also asked to mention that I am an Orion+ member.)