2010 Audi A3 Sline injector problems

[ianson2222]

Hi thanks in advance, I have a customer that came into me with bad 2 injectors they were tested via vagcom and removed no1 was stuck in and had to have a specialist in to remove it. reconditined Injectors then were fitted with new copper sealing washers. Car got a mile leaving workshop and it had stripped thread of clamp bolt. We then helicoiled hole and fitted a new bolt. This time car lasted a week before clamp bolt came loose, it was locktites in and had locking washers on, but helicoil is only a short thread compared to original thread. What would be best course of action, retap hole 8mm and try again or is therean underlying problem why injectors are coming loose? Thanks In advance Ian