Can't open runes in Megaltih unique map after leaving once

It's my first time doing the megalith unique map. I finished the bosses and started to loot the runes. After opening some of them my inventory was full, so I left the map to make some space.

After coming back the runes could not be targeted anymore and I cant get the other half of the loot.

At the time I was in a party with my girl friend. So I am not sure if this bug is a interaction with party play. Though she was not even in the map before this happened. She just entered it later to see if she could open the runes.

For me the runes still glow as if they were active. When she entered the map later they were not even glowing for her.