Bug Unity opening persistent, blank windows on script compilation

Updates

Update 2: This seems to be caused by one of the Dynamic Shadow Projector package's URP/LWRP-related extensions. See this URP extension issue or this projector feature issue for details.

Update 1: This also rarely happens when entering play mode, even if no scripts were changed since editor restart.

Description

When I save a script, Unity often opens an extra, persistent, blank (white) window after compilation. These pile up over time. I've tried deleting the C# project files and solution. This occurs even when saving scripts with text editors other than Visual Studio. Anyone aware of what might cause this?

Screenshots

Taskbar, showing a bunch of blank windows:


Task manager, reporting a status of "Not responding" for a separate Unity Editor process:


Versions

Unity 2021.3.2f1
Visual Studio Community 2019, 16.11.16
Packages > Visual Studio Editor: 2.0.15
Windows 10