Intermittent pseudo-crashes

On multiple machines, and multiple OSes (Mav, Yos), I intermittently get the following incorrect behavior.

In a terminal, type mvim abcd where abcd is some non-existent file.

Expected: I get a MacVim window with an empty buffer that is assigned the name "abcd".

Actual: Most of the time I get what I'll call a pseudo-crash. All MacVim windows vanish instantly with no offer to save unsaved changes, and MacVim vanishes from the Dock. However, there's no crash report. The only clue as to what happened is in Console.app, and it's a meager clue at that:

Vim: 07/21/15 2:15:23.551 p Vim[89294]: -[MMBackend(Private) connectionDidDie:]@2315: Main connection was lost before process had a chance to terminate; preserving swap files.

It can also happen if I am already in a MacVim window and I do :edit abcd (where again, abcd is non-existent).

Is anyone else getting this? I see that someone else reported the same error message in Console but in a different context on Feb 19th of last year, and that Bjorn didn't know what it meant.

I can't find a way to get 100% reproduction. It tends to come and go in "streaks", i.e., a few hours of pseudocrashes, then a day without them, then two days with, then a few hours without, etc.

At first I thought maybe it was because I have Spotlight disabled (using mduitl -i off or mdutil -d), but I tested this theory by reactivating Spotlight and I still see the problem. (And surely MacVim doesn't need Spotlight to be on. I've had Spotlight off for years with no problems like this).

Start by exercising the reported entry points: run mvim abcd for a nonexistent file and try :edit abcd in an existing MacVim window. Review the Console.app message about MMBackend losing its connection and compare behavior across the reported macOS versions. Done means the pseudo-crash is reproducible and the underlying failure is identified and prevented or properly reported.