Soundwave got excited and hugged Galvatron and without thinking tried to shove him in the chest too, forgetting this son doesn't work like that. And is also a fair bit bigger than him.
Or as StarryTiger put it “Confused space opossum does not understand why the big baby won't fit in the pouch”.

They stayed like this in silence for a good while, mutually agreeing that they'll never speak of this again. At least until Rumble and Frenzy share the photos they've taken.

For those new, in this AU/timeline Soundwave adopts Galvatron as his son, Rumble and Frenzy are cool with their new purple bro.