MacVim opens from Terminal (mvim) but does not render interface from Finder

• macOS Big Sur 11.1
• MacVim Custom Version 8.2.2164 (169)

VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Dec 19 2020 21:23:05)
macOS version
Included patches: 1-2164
Compiled by root@Mac-1608412769109.local
Huge version with MacVim GUI.

This is macvim: 8.2.2164,169 (auto_updates) installed as a cask from Homebrew.

When I launch MacVim using the mvim script from Terminal, it launches the app and renders a GUI window. Everything is as it should be.

But when launching from Finder (either Cmd-space and typing MacVim.app, or double clicking the app bundle from the Applications folder, the app runs; it creates an icon in the dock, it presents a menu, but it doesn't render a window for the editor. Cmd-O opens a dialog to select a file to open, but opening a file does not render an editor window for the file. The Window menu does not list any open app windows. It's running and responding appropriately, but not rendering a window when launched from Finder.

I've seen this behavior in several macOS releases now over the years. It's sporadic. When the issue occurs, it's frustrating and I move on, but at some point I switch back to the MacVim task and open a new window, and it just works as if there was never an issue.

As an experiment I backed up and removed my existing .vim/, .viminfo and .vimrc which are customized. Afterward, MacVim launched correctly (rendered windows) from Finder. I'll review settings but it's not clear to me why a customization would cause failures running from finder vs. running from start script in Terminal.

Start by comparing MacVim launched through the mvim script with MacVim.app launched from Finder, using the reported .vim/, .viminfo, and .vimrc customizations as the main variables. Reproduce the missing-window behavior with the user's configuration, then identify which customization or launch-context difference prevents the editor window from rendering and verify that Finder launches work without removing unrelated settings.