Failure to go into battery every time

[spangy]

Originally Posted by DonVoigt

You should replace the damaged breechblock. the missing areas serve to retain and limit
motion of the extractor and are a likely source of your problem.

Breechblocks are not inexpensive, but important for function and safety.

GT can do this for you.

100% agree DV .... A long shot but make sure you have a fluted firing pin ... The non fluted is original, due to primer rupture and blow back that would destroy the firing pin and sometimes the toggle. They replaced them with a fluted pin that has a grove to allow gas to escape and this might have accounted for the original breech block damage if it occurred.
And having Dr.GT look @ it is an offer too good to refuse in my book .... good luck M8