So I tried to go to shops to get this bug fixed, I was quoted £30 for the previous update, but I was warned that the previous update might not work.
I've rebooted 5 times in 2 days (almost 3) and it's still happening.
Shops won't do Cache Partition but will charge me £30 for previous update which is pointless as it'll happen again.
When it locks I've noticed it won't let me answer calls, very frustrating.
Samsung still hasn't replied to me, not that that's any surprise.
So now I've got to stick with this until I get a new phone.
One disgruntled Samsung user.