Moving around in cot/crib

K ✨
Hi ladies,
So Samuel will be 6 months on the 30th. Over the past few nights he has decided it would be fun to wake up several times during the night and crawl/shuffle around the cot.
It freaked me out the first time as I looked at the baby monitor and I couldn't see him because he had wriggled to the top of the cot!! 
Is anyone else's babies doing this? 
He is a tummy sleeper and just rolls around everywhere. I've tried sleeping bags, tucking him in super tight but he just worms out like a little Houdini baby 😂
I just purchased a sleeping bag called the "baby ok sleeper" which is a sleeping bag with a sheet attached to it so he can't wriggle up or down ( he can still roll and sit up). This won't arrive for a few days so the next few nights are going to be fun !! 👎