Longstanding Solitude stacks in co-op drastically increased xp for next level

[Choris]

It was 4 stacks in co-op with my 2 friends.

We were stuck at late 40's while enemies were 60+
Chests were around 7k at 40 mins and killing grandparent (lvl 60+-) gave like 1-2% ( we were lvl 48)
And yes we were killing them pretty fine. Just died later from tp bosses. Another grandparent roasted all my hp with 4 stacks even after i hid from the sun.
Guess xp is broken and somehow decreases greatly from stack amount???

[iron]

Having this experience as well. Do you think it only occurs from stacking them? Or is the item just bugged on a base-level?

[Choris]

Seems like stacking problem.
Has coop run just now and 1 item worked as intended.
We got 94 and died in void fields. Nothing unusual