It was structured with standard verbeage that mortgage to be discharged on or prior to closing . I doubt that they look at this deep enough at rofr time to see that what is being sold is only part of what’s mortgaged, that’s what title company does, and they will likely flag this to MORi and go back to seller at which point the different contracts will be coordinated - seller is obliged to discharge mortgage fully on each of the exercised contracts, thus the various contracts will have to get processed at same time.