This is a walkthrough of exactly what I didI'm following the main storyline. I'm doing the mission 'A cornered rat' in-which I have to go to 'Riften' and talk to 'Brynjolf'. Doing so, I learn that he'll only help me if I help him first. So I unlock Modesi's stall and unlock the chest that contains the ring. I then plant the ring with 'Brand-Shei'. After successfully planting the ring it tells me to speak with 'Brynjolf'. I do so and he tells me to meet him in the 'Ragged Flagon'. I immediately go to the 'Ragged Flagon' in which I notice he's currently not there yet. I walk around the area and talk to all the people; I talked to bartender in which I bribe him 487gold coins or something to give me the information (I then received an 'Achievement'). I then find Esbern and bring him back to Riverwood which completes said quest. After which I go back to Riften to finish my previous quest; I go back to the 'Ragged Flagon' and I then wait every hour so that I don't miss the moment he actually goes there. After 48 hours, I'm doubtful he's actually coming. I go back to see that he's still standing in his 'stall'. It also seems as though the merchants are still 'distracted'; 'Brand-Shei' is still sitting on that box and everyone is looking at Brynjolf.
I've tried attacking Brynjolf hoping for a reset; No luck.
I've tried purposefully failing a pick-pocket from 'Brand-Shei' which caused me to be attacked but eventually they all went back to the same spot when it was all over.
I'm extremely frustrated.
I'm hoping that this detailed 'walkthrough' helps in reproducing this problem.