My son did this too 😂
They very often stop making old sounds while they try to master new ones, and then the old ones will come back in again. You'll find the same with things like clapping and waving etc, they'll pretend they forgot everything they learned so far, because they're busy learning something new.
Blowing raspberries is a normal milestone 😊. My daughter has her first teeth coming and the raspberries are back in full force as part of her teething
Yes 😂