I agree, it seems like they are leaking off oil pressure. This evidenced by them only clanking at hot idle. At higher revs or when cold they have plenty of pressure to keep up with the leak.

I think the problem may be wear in the adjuster cylinder bore, although I can't confirm this. I lean toward this conclusion because the adjusters seem to go into clanking failure mode more often on cars with previous oil pressure issues. And I've seen them fail soon after a single low oil pressure event (ie: "finishing off" the adjuster). Just my speculation though.