Disclaimer: apologies if this has already been answered elsewhere.
On the group finder you can opt for a random dungeon selection for a healthy amount of EXP once a day in comparison to requesting a specific dungeon. Normally, if you go to do this again the same day, you get offered a much lower amount of EXP (approx. 30%). This is nothing new.
But, every now and again (last night being one example), even though I've completed the random dungeon and got the EXP lump, I can go on random dungeon again and still get the full EXP amount. I did 3 in a row last night.
Is this a bug? Or if it's an intended feature, how do you know when it will happen? I.e. is it a given day of the week / do they stack up to a limit / is it completely random and down to RNGesus?