Visual Studio Code and Tahoe 26.4

Hi all, Wondering if anyone else has noticed a degradation in performance between VS Code and Voiceover in 26.4? I'm finding that in some files (primarily Markdown), when I use the up/down arrow keys to read-by-line, VO does not read the line but instead reads random characters. I have checked the various accessibility settings, and it is optimised for Screen Reader. To be honest, it has been so long since I set it up on my previous Mac that I have forgotten any additional steps that I may have gone through, and as this is a new machine I suspect that I've overlooked something. It may be as simple as installing a Markdown extension or something, or disabling some syntax highlighting, but I'm not sure. I have my entire 11ty project (including Markdown) in one codebase, so I'd rather not use a separate editor for bits and pieces of this. Anyway, if anyone has thoughts I would appreciate hearing them. cheers.