Trapped Solid Chest in back of Screeching Canyon cave in Thousand Needles?

This is on Classic Anniversary Nightslayer.

I write this as I am running back to my corpse in the back of the Screeching Canyon cave. I spotted a Solid Chest in the very back while scouting for ore and figured why not. So I clear all the harpies within aggro radius (I'm level 32) and have at it. Suddenly 3 harpies ambush me and I fight them off. I loot the chest again after double checking for any nearby mobs, and watch those same three harpies respawn and attack me. I hadn't bandaged, wanting to beat respawn timers, so they finished me off quick.

I have never seen a chest like this before. I'm not sure it's possible to open since the harpies will spawn and interrupt you.

Maybe there's a workaround but I'm not crazy enough to risk more corpse runs.

Anyone experienced anything like this before?