The source was the PL. They leaked it to recover some credibility/move the noise towards the buyers probably through frustration at getting insufficient/unclear data from the 3 sets of lawyers working the deal.
The whole thing is a clusterfuck.
BBC running with ‘gridlocked’ now. PL clearly leaking this to pressurise the buyers into action. The issue of going through three sets of lawyers for the buying consortium is clearly a problem imho.