ssh broken pipe problem

[James Walker]

When I say "hg incoming" in a repository that should have nothing 
incoming, I'm getting a result like this:

   comparing with homeserver://notes/
   searching for changes
   abort: stream ended unexpectedly (got 16323 bytes, expected 32768)
   remote: packet_write_wait: Connection to <redacted>: Broken pipe

(The exact number of bytes it "got" varies from one try to the next.)

Whereas "hg log -l 3" works fine.  Googling this broken pipe error 
mostly leads to discussions about an ssh session failing after a period 
of inactivity, which I don't think is the issue here.  If I start an ssh 
section interactively, it seems to work fine.

The version of Mercurial on the local host (on macOS 10.15.2) is 5.1.2. 
The version of Mercurial on the remote host (Linux Mint) is 5.0.1.

When I tried making the ssh command be "ssh -vv", I saw a bunch of 
legit-looking debug lines before the "comparing with" line, but no debug 
lines after.

Any idea what could be wrong?