A few thoughts - is he going through SA? If I recall correctly ds1's worst SA was right about 19 months, I could literally not leave the room, in particular for naps. At day care (3x a week) he was completely fine going to sleep. It manifests differently for every lo though, so just a thought?
My ds2 is slightly younger but also just in a phase where if he does not like something he will scream, kick, scratch etc. When this happens I learned my lesson from his brother not to fight it, but to start over. So if it were a nap time, I think I would take him back out to the living room for a little while, 10 min or so, then start talking to him about sleepytime and take him into his room.
By the way, ds2 is also going through SA atm and when I start leaving the room he will stand up and scream. Just about the second I walk out and close his door, he is 99% of the time quiet again. The other 1% is when we have to "reset". I did WI/WO with his brother with great results too btw - I just usually don't have space for the consistency it requires during the day because his brother is home too.