can't claim rewards on unique map after dying

I was doing the unique map where you have to summon a bunch of bosses on the rune. I didn't claim any rewards for the first 6 or 7 bosses, so I could claim all at the end.

However, I died on the 7th or 8th boss and can no longer claim any rewards from the first 6th or 7th bosses.

Is this buy or by design?