Ammo can make a difference. Try different loads; shoot it from a bench; have a really good shooter try it also.
Good luck
Jerry
Sorry, but 25 feet is 8 yards. NO ammo is going to be that bad, that close.
I am going to go with trigger and recoil of the .40 affecting reset of his sight picture. And firing too fast.
Give me an hour and I could get him shooting at least silver dollar sized groups at 8 yards with either of these.
Shoot that SIG again with loading 1 round at a time. I guarantee you would tighten that group up considerably. There is no reason to have a shot pattern like this at 8 yards, with any pistol. Except for firing too fast.