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?

在 macOS 10.14.3 的 MacVim 8.1.950 中重现该问题，将 Escape 与 Ctrl-[ 以及 terminal Vim 和 VimR 进行比较。跟踪 MacVim GUI 对 Escape 键的处理；当 Escape 能够可靠地退出插入模式，且不影响其他 Vim 环境中的正常行为时，即可完成。