Why Does DynDOLOD not render properly suddenly?

https://loadorderlibrary.com/lists/preserveartdirection

The billboards do not render beyond the line visible in the screenshot below, and they will pop-in suddenly when the line is approached.

https://i.imgur.com/SZzj2eR.jpeg

I've been using DynDOLOD and NGIO for about a year now without issue. Suddenly, the distance grass shows a noticeable line with pop-in. I changed nothing about my load order between the two sessions that were about 4 months apart (I was away from home).

I've tried regenerating the grass caches twice with NGIO, and I've reinstalled DyNDOLOD twice now. I've double-checked the GrassControl.ini. I even tried recovering my Skyrim and Vortex installations from my backups, but even the backups have the issue.