Nikon F2 DP-1 finder problem: speed cannot change

Just got a bargain sold as is from yahoo. Everything works fine without the finder, but the dp-1 cannot work properly. I can neither lift the ASA ring to set film speed or rotate it to change shutter speed,. I can change shutter speed with the dial on the body so I can just purchase a 3d printed waist level finder but I still want to repair the original finder if possible. Anyone has sandy suggestion or encountered the same problem? Thanks!

There could be any number of reasons why it does not function properly; too many to guess.

Maybe someone just took a DP-1 with a destroyed metering system and glued it down to have use of a reflex viewer, when the non-metered prism was not available to them.

Here is the service manual. It may point you in the right direction if you are mechanically inclined...