Escape key no longer works in MacVim

I am running MacVim 8.1.950 and macOS 10.14.3. Somewhere in the last couple of updates, or perhaps after upgrading to Mojave, the escape key quit working for me when using MacVim. If I am in insert mode and press escape, nothing happens. Ctrl-[ does work, and I can also do :map ii and use that. But this is a huge hassle after decades of using Vim.

In terminal, on the command line, escape works in Vim. In VimR, escape works in the gui. I have only noticed the problem when using MacVim. It was also happening on at least one version prior to 8.1.950. This problem has been persistent for a while through multiple upgrades to Mojave and to MacVim.

Any suggestions?

macOS 10.14.3 上の MacVim 8.1.950 で問題を再現し、Escape と Ctrl-[、および terminal Vim と VimR を比較します。MacVim GUI における Escape キーの処理を追跡します; Escape で確実に挿入モードを終了でき、他の Vim 環境で機能している動作に影響しなければ完了です。