Diesel injector clamp / fork snapping

[mbglos01]

Hi all, hoping to get some advice on an issue. 

I have 2011 (mk3) Ford Focus 2.0litre diesel duratorq. 

Since April I have been having issues with fumes in cabin. Closer examination showed exhaust fumes was coming from around 1st cylinder injector and into air intake. I thought it was injector seal which had gone, so had them all replaced at Ford Main Dealer. At the time of the repair they had to replace the clamp/fork which holds the injector into the engine. One arm of the clamp had sheered off. No fault codes on the engine were present 

Since then this clamp has failed 4 times on cylinder 1. And this time cyclinder 2 clamp/fork has also failed. 

The first couple of times ford suggested they had over tightened / under tightened the clamp bolts. But for the last couple of times they have torqued them down to the recommend tightness. 

They say this is a type of fault they never see.

Has anybody else had trouble with this? 

Other than over/under tightening the bolts, faulty parts or missing other parts does anybody have any idea what could cause this? I wouldn’t think there is too high pressure in cyclinder causing this - as the clamp surely wouldn’t be the first part to fail.

Appreacite any advice / information anybody has.