Well-placed sources connected to Caesars tell TMZ ... the company is sitting on $150 million for the run of the residency -- that's the astonishing amount the show would generate. As a result, Caesars and Live Nation want to figure out a path where the concert can go on. We're told they need to figure it out -- one way or the other -- in the next month.

Our Caesars sources say they're not sure if they can reach an agreement with Adele, because there was significant conflict over numerous issues connected with the show over the last 2 months, including the sound system, the choir, a special effects pool, and on and on.

Our sources say Adele was unhappy with the outdated Meyer sound system that was in place at Caesars' Colosseum, so the casino installed an entirely new state-of-the-art sound system ... and Adele was happy with the upgrade. But we're told there are a bunch of other open issues which are still a source of conflict.

But, that obviously wasn't enough to save the show from going on as scheduled ... and now we're told even Adele's boyfriend, sports mega-agent Rich Paul, is involved.

Caesars initially hoped they could work something out so Adele would do at least a few concerts in February, but that's not going to happen. They're now shooting for mid-year, assuming they can reach an agreement fairly quickly.