malloc errors in psql with libpq 16.1 on Mac

I have a colleague trying to use psql to connect to a remote DB, but he's
getting this error:

FATAL: no PostgreSQL user name specified in startup packet

psql(42705,0x7ff84a07b700) malloc: *** error for object 0xa6: pointer being
freed was not allocated
psql(42705,0x7ff84a07b700) malloc: *** set a breakpoint in
malloc_error_break to debug

He was using psql 14 and we upgraded him to psql 15 but no change. I
noticed he was on libpq 16.1 (installed via homebrew). Another colleague
who was able to connect fine was on libpq 15.3. He upgraded to libpq 16.1
and boom he now gets the same error.

One colleague is on an older amd64 Mac, the other is on a newer arm64 Mac.
They are working to try to pin the older version of libpq but this is
probably going to bust out to a larger group as other homebrew users run
their routine updates.

Just wondering if anyone else has had similar experiences or if this is a
known issue?

--
Don Seiler
www.seiler.us