Talking

I have a couple questions about talking. My son says a large number of words and can say some 2-4 word phrases. However, several of his words and phrases are very difficult to understand. I’m the only person who knows what he’s saying when he says certain things. My husband is getting better at it but still has to ask me sometimes what he’s saying. For example - “open” is meh-nah. “One more time” is mah-nah-nah (and he waves his finger to indicate one). The way he pronounces these words is consistent every time, so I know what he means since I have figured it out over time. When he says something that is hard to understand, I always repeat the word back to him the correct way and try to encourage him to say it correctly.

Is this normal or should I bring it up to our pediatrician? Anyone else’s 20 month old similar?