The facts are Dr Sun was paid half in cash and half in scrip for...

The facts are Dr Sun was paid half in cash and half in scrip for the remainder of what was owed to him for sbl.

The loan sbn is now talking about is (my assumption here) the funding sbn provided to sbl whilst it continued to operate at a loss.
Since they have now closed sbl then sbn is calling that loan in so to speak.
Security for that loan was the patents etc.
This is a formality in my book as in simple terms its the same as repossesing a house, even then you still call in lawyers.
If the Suns do fight it (something i doubt) they have virtually no chance of winning.