Banging/Clanking Noises in high rise steam system

I live on the 43rd floor of a high rise apartment building in NYC. The building has a steam boiler and in my apartment I have a two pipe fan coil system and a PTAC. There is a riser in between the two bedrooms. For many months we have been hearing loud banging or clanking noises for about 10 seconds at a time, sometimes as often as hourly when at night. We no longer use the actual heating system and the noise still occurs. During this period the building has changed the coils, steam traps, and other parts in hopes of fixing it but nothing works. Most recently they dropped the pressure on the boiler from 3.3 psi to 1.9 psi but it doesn’t seem to have helped. Their next idea is to replace the expansion joint because my floor has them and other units up and down in the line don’t complain about this issue. I’m skeptical that is the fix but we’ll see.

Can anybody please help us figure out how to get rid of these noises? We cannot sleep at night and we have a baby that also wakes up from the noise constantly.

Thank you!!