Old yet crazy

[Selma]

Hello
So i currently own an official senior syrian hamster at 18 months old. He is super healthy and happy, but i have noticed that he has started to act a lot more crazy lately. Whenever i put him in his playpen (which is stacked full with toys) he always tries so hard to escape and never gives up. It gets to the point where i'm forced to put him back in his cage cause it's just not enjoyable at all to have him out. It's weird cause usually hamsters slow down with age but he has just sped up considering how lazy and slow he was when he was younger. Just wondering if anybody has any explanation about this behaviour, and if anybody possibly has dealt with this behaviour before.
Thanks!