Quick guide to the Uninvited Guest Party Quest!

I'm wondering if it sends you to the instance version in numerical order... To make myself more clear, bad pseudocode!

If (party1 enter) && (instance1 isEmpty) then
send party1 to instance1 else
if (instance2 isEmpty) then
send party1 to instance2 else
...
...
fi

That could explain why your trials always give the same chests for the same portals? Knowing Nexon, it seems they'd take this easy way out instead of randomizing which instance the party gets thrown into. Of course, I haven't tested it either so I'm not denying what you said either.

Would looking at reactors in the data be able to tell us?