I have changed the health check script so it uses
	dig -b localhost @localhost
which makes it set SO_REUSEADDR, and this allows its connections to
succeed when they fail without the -b.

That sort-of confirms my belief that this is a bug.

There might be tuning I can do elsewhere to improve the situation...

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
Southeast Iceland: Southerly veering southwesterly 6 to gale 8, occasionally
severe gale 9 in west. Rough or very rough, becoming very rough or high. Rain
or snow, then snow showers. Moderate or good, occasionally very poor.