Originally Posted by Lumatic
The OEM lock is a Bargman KT 200. Parts and replacement are available but are very expensive. You can get parts or send the lock for repair to Inland RV. Inland RV also has a less expensive lock replacement kit. From your description it sounds like a small tang is not engaging the notch in the shaft which moves the deadbolt. A photo of the inside of yours would help but maybe these photos will help.
The lock Airstream used from 1970 to 1977 was made by a company called, "KT".
They never had a relationship with Bargman.
The Bargman L-200 lock was used from 1966
The L-200 inside handle was very prone to breaking, therefore the L-100, that has a round knob on the inside, has been used as a replacement.
The only difference between the L-100 and the L-200, is the inside handle/knob.