discovery 300

hello ive just joined , iam having a problem discovery 300 tdi . For some reason a few months ago it slipped cam belt . Did abi of damage i have had new belt and pully upgrades push rods had been broken so replaced with a new set . allput back together , ran it for a wk and it snapped a push rod again . replaced set again , and the same thing has happend again after 3 days . its now getting very expensive . Can any one shed any light before i change the engine . thankyou Phil.

The rocker shaft has a problem.

Its either broken or bent, or the adjusters are loose allowing too much movement. Are all the collets in place on top of the valves?