I'm hearing "după-amiază" as "dupamiază." Is that how it should sound? My recollection is of după-amiază having 6 syllables, and not an elision / liaison, but maybe I'm wrong? Or is the 'lost ă" still there, but so subtle that I'm just not hearing it, like the almost silent 'i' at the end the end of a word like 'suni'?
Both pronunciations are correct.
I personally pronounce it like the recorded one, basically dropping a sound and saying something exactly like dupamiază instead. I think that's the reason why we write these two otherwise distinct words with a dash in between.
Perhaps in some regions of Romania they prefer the more verbose pronunciation, but I'm used to this one and I like it cause it's shorter (like two syllables less).