Remote (CentOS 8) X11 clients stop spawning on local (FreeBSD 12) X11 server over ssh after some time

[parv/freebsd]

Hi there,

I had started ssh -X connection 2+ days ago in X11 on FreeBSD 12-STABLE to
CentOS 8.
When I tried to run Firefox (on CentOS), it did not start & blurted ...

  Unable to init server: Broadway display type is not supported:
localhost:13.0
  Error: cannot open display: localhost:13.0

... tried evince, did not start & barfed ...

  Unable to init server: Cannot connect: Connection refused
  Cannot parse arguments: Cannot open display

OTOH, on a few moments old connection Firefox & evince open respective
window as expected.

What is going locally and/or remotely that after some passage of time,
clients fail to
connect to $DISPLAY?

- parv

--