mosh sometimes hangs on connect

Sometimes, when I try to use mosh to connect to a VM running on my computer, mosh just prints a couple of blank lines and does nothing else:

moth ~ $ mosh h4 

(h4 is the VM.) Ctrl-c and ctrl-\ do nothing. No mosh TUI with a blue banner or anything; it's as if I typed echo;echo;cat>/dev/null and somehow disabled ctrl-c and ctrl-\. pgrep shows there are three mosh-server processes on the VM and no mosh-client processes on the host.

The host machine (i.e. mosh client) runs OpenBSD-current amd64. The VM runs OpenBSD 7.3. Both have mosh 1.4.0.

Here is an excerpt from pstree output on the host where I ran mosh h4:

 |       |-+= 40796 falsifia /usr/X11R6/bin/xterm
 |       | \-+= 25909 falsifia ksh
 |       |   \-+= 36986 falsifia perl /usr/local/bin/mosh h4
 |       |     \-+- 11626 falsifia ssh -n -tt -S none -o ProxyCommand='/usr/local/bin/mosh' '--family=prefer-inet' --fake-proxy -- %h %p h4 -- mosh-server 'new' '-c' '8' '-s' '-l' 'LANG=en_CA.UTF-8' '-l' 'LC_TIME=C' '-l' 'LC_COLLATE=C'
 |       |       \-+- 36023 falsifia perl /usr/local/bin/mosh --family=prefer-inet --fake-proxy -- h4 22
 |       |         \--- 54912 falsifia perl /usr/local/bin/mosh --family=prefer-inet --fake-proxy -- h4 22
 |       |--= 15846 falsifia emacs (emacs-28.2)

This bug isn't consistent: usually mosh h4 successfully sets up a remote session on h4.

I don't think I've observed this when connecting to a machine that isn't a VM on the same computer. (I wonder if it's got something to do with network to the VM being super low-latency.)

I saw https://github.com/mobile-shell/mosh/issues/114 which looks quite similar, but it's old and closed, and I'm running mosh 1.4.0 on OpenBSD.

Start by reproducing mosh h4 on the OpenBSD-current host with the OpenBSD 7.3 VM, then inspect the pstree and the mosh-server/mosh-client process state described in the report. Compare successful and hung connections, including the SSH command and low-latency VM network; done means the intermittent connection completes reliably or the failure is diagnosed with a focused regression test.