Hey there, 'Keep of Honed Edges' is the likely suspect. I am not sure 'why' it causes issues, but back when I was trying to do the speed challenge for it, I had to complete it multiple times. It took several goes at it - the first run completed Petra's bounty just fine, but it's only the final run (5th or 6th) that actually counted for the 'Honed for Speed' triumph, AND finally completed 'Ascendant Champion' which hadn't popped during any previous run. I see this one just happens to be this week's challenge, do you know if Ascendant Champion was showing 4/6 before you ran it? (Speculation! Keep of Honed Edges has multiple configurations, there are different start points in its arena. So I suspect that only one variant actually counts for the triumph. I see people say you must take the sword through the portal at the end, but I did this with each run and as above, even the standard completion triumph didn't pop until I'd had several completions of it.)