What often happens on the older door latch mechanism is the tiny spring
inside that holds the button either up or down breaks. Then gravity makes
the button drop down, into the locked position. But you can still open the
door using the key to hold the button up while you pull down on the handle.
The spring is inside of a sealed assembly and not trivial to access.

There is a simple workaround it this turns out to be your problem. Just get
a piece of hose or tubing that snugly fits over the button shaft. Push it
against the door. That friction will hold the button up instead of the dead
spring.

Thanks, Mark. But the lock button doesn't seem to be the problem. And
regardless of the key position the handle won't open the door. At this
point I have the handles and lock cover off, but in order to get the lock
assembly out I need to have the door open, and that's what I can't figure
out how to do. I don't have an exploded view of the lock mechanism to refer
to. Anyone have any ideas on getting the door open?
Many thanks, David
'83 Westy
'61 BMW R r69S