May be repeating what has already been said..
108m is a huge amount. Any deal of that money across any industry, any country will involve top level negotiators...if seller wants to sell and buyer wants to buy. In case of Sancho if Dortmund not sending some of their own top hierarchy and sending some two bit representatives indicate they are not serious.
Another point, if a party is not serious about selling but reluctantly engaging somehow, possibly because Sancho wants to leave, then it will set some ridiculous conditions like no performance bonus, all guaranteed money etc.
So, it is best for united to move on and focus on business where there is a chance of success. If Sancho had to happen it would have happened by now. We will come back on some other day.