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?

Reproduziere das Problem in MacVim 8.1.950 unter macOS 10.14.3 und vergleiche Escape mit Ctrl-[ sowie mit terminal Vim und VimR. Verfolge die Verarbeitung der Escape-Taste durch die MacVim-GUI; die Untersuchung ist abgeschlossen, wenn Escape zuverlässig den Einfügemodus beendet, ohne das funktionierende Verhalten in den anderen Vim-Umgebungen zu beeinträchtigen.