SISU is Otium. Same people in charge. The golden share needed to play in the football league was registered with one arm of the company, whereas the players contracts were registered with a separate arm. SISU appointed their own administrator, and because the majority of the debt is owed to themselves, they could offer way more than anybody else, hence the administrator favouring them.
From what I can gather, SISU are trying to completely destabilise the Arena Company so they can get hold of it for a steal. The casino company are already threatening to leave if Cov do play their games in Northampton, and the catering firm Compass paid something like £40 million for the catering at the Ricoh for the next 50 years, I doubt they will be too happy either.