Pure of heart Glitch

Hey, just wondering if anyone has encountered a glitch for the Pure of Heart achievement for defeating Nidhogg? I’ve done it several times now without using an elkshrine and even without drinking the wine from the sommelier or buying health from the wandering trader. Also without my summoned courage kicking in. And the achievement is not showing up. Last time I even got through the whole thing and defeated Hel without any healing. Any suggestions?