UBB.threads PHP Forum Software Community Forums UBB.threads 7 Bug Reports Fixed Bugs [FIXED for 7.5.1] 7.5 Change Groups Problems

I am using 7.5

I used member managment to find a group of users by last on date,
I selected all members in search,
I selected Change Groups,
I selected which group to remove and which to add,

then I recieved the error.