Big Sur / Can't open windows from finder properly, but works on terminal

Describe the bug
When I open a .tex file on MacVim from the Finder's level (just by clicking on a file), I get an error:

On the other hand, when I open the file form terminal, ie. mvim <file_name> it opens properly and every plugin works, as on MacOS Catalina. This strange behaviour emerged when I updated MacOS.

To Reproduce
As written above:

1. I open a file from Finder - error pops out and actually nothing works (just like it was disconnected from anything that is installed and configured by .vimrc)
2. When I open a file from terminal using mvim everything works as it should.

Expected behavior
No such errors, consistency between opening from terminal and finder.

Environment (please complete the following information):

• Vim version: VIM - Vi IMproved 8.2
• MacVim version: MacVim 8.2.1719 (up to date)
• OS: macOS Big Sur
• Terminal: GUI, Terminal.app

Additional context
It emerged after system update from Catalina to BigSur.
I have MacVim installed from .dmg file.

まず、Finder からの MacVim の起動経路と、ターミナルからの mvim の起動経路を比較します。報告されている .vimrc の読み込みの違いと、MacVim 8.2 の環境を再現の基準として使用してください。macOS Big Sur で動作を確認し、その後、GUI 起動のエントリポイントを追跡して、同じ設定済みの動作が Finder からエラーなしで機能するところまで確認します。