In Her Defense instance fight broken

Time: 22nd June after 8 AM (GMT+3)
Frequency: both times I tried
World name: Balmung
Character name: Sharcos Dea
NPC/Monster name: Rosalinde Bloodfang
Party or solo: solo instance
Steps:
1. enter the NIN job quest In Her Defense instance on Hullbreaker against Redway and Rosalinde
2. defeat Redway as per normal
3. at a bit more than 60% of her HP gone, Rosalinde uses Holmgang on player, and keeps spamming Holmgang on the player thereafter. The NPC helpers are unable to defeat her despite getting her HP bar empty, and the player is stunlocked due to Holmgang spam
4. The instance eventually times out because nothing can be done

I first suspected a disconnect from the server (...a very weird one!), but since I didn't want to wait a couple hours in queue to get back in, I waited out the idle timer in the instance and it spit me out normally back to Moraby where players were running around, and at no point during the fight did NPC helpers stop doing their attacks (including weaponskills and ninjutsu alongside autoattacks). Besides, twice at the exact same part of the fight...