Puppy pees his bed – help?

Hi! I’ve gotten better at watching my 4 month old pup and knowing when he needs to go based on routine and his belly lol. Accidents have gone down to almost 0 in the course of 3 days but he just peed on his bed in the crate even though I put him in the playpen where it’s covered with peepads.

Can someone tell me why he keeps peeing on beds? Or no beds for him till he’s older? I previously cleaned the bed with enzymatic cleaner and he even slept on it without peeing on it last night.

I realised he also likes to lie down in said pee on the bed. Sigh. Does anyone understand his doggy brain? I need help with translation.

Thanks!

NOTE – just fully vaxxed cannot get on grass, no fresh patch in house either.