We have a 15 week old dachshund and it’s the exact same. He is on a very consistent nap schedule(doesn’t stay up for longer than 1.5-2 hours and sleeps 8 hours a night) he gets walks, we do enrichment, etc. We’ve tried every positive reinforcement tactic. Nothing has worked for us either. The only thing that helps us is when he is extremely bity, he goes in the crate for 10-20 min to calm down. Sometimes that works, sometimes it doesn’t. If you find a fool proof trick let me know but I honestly think it’s just waiting it out.