EXPECTED: boss dies, drops loot and popup to summon portal appears
INSTEAD: boss dead, nothing happens: https://imgur.com/a/UiHFrjO ( quest marker still active )
happened only sometimes as long as i had a bugged char, resolved after deletion of bugged char. problem occurred with forges as well. have some more pictures if needed.
edit: just noticed this might be duplicate / related to: Monolith of Fate Completion Bug