Bent rocker push rods...twice... HELP

Hey all,
So I just got my 1989 County 110 diesel motor rebuilt. Drove it home a few days later I downshifted from 4th to 3rd approaching an intersection. It made a few odd rushed sounds, then died on me. It would turn over, but not engage. The mechanic towed it back to his garage and informed me I needed 8 new rocker push rods (I'm not sure of the exact technical part name, so bear with me.) A few...well a lot of weeks later I pick it back up.

A couple days later I drive it 60 feet and it does it again. 2nd gear, not high revving or anything stupid like that.

Firstly, I've never heard of this mechanical problem, odd. Secondly, why twice in a flipping row. The mechanic is going to pick it up Monday, and I wanted to see if any of you all could piece together the most likely cause of this Landy hic-cup.

Thanks for any imput. Cheers Hank

Valve timing, and valve clearances are first things to check

O dear was it set up using the rule of 9 ?? timing belt slipped perhaps??

Thanks Freelance, and Kevstar, I will translate your suggestion to French for my mechanic, it makes sense. It was sounding like it was way off, and building up pressure.

Fairly sure you measure piston height, and choose the thickness of head gasket to suit

not on a 19j theres only one head gasket, things to look at are
timing belt/timing
cam follower rollers, if they 50p its difficult to ensure good tappet setting
follower guides and brass followers guides can wear so follower jams

Get a new mechanic.