I would check a few things.

Try adjusting the bowden cable. It is attached to to the top of the valve cover. It is a cable with a red rubber boot on it. It can be turned and it adjusts the shift points. This probably won't help.

Also do a search on the forum for the linkage involved with the gear selector. It could have broken bushings.

Are you having any other vacuum realated problems?
Doorlocks not functioning.
The engine not shutting off.
Etc..

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