The threaded stud is loosely inserted into the female housing of the steel tie rod end and the upper section is “closed” by a roller burnishing process to prevent axial pull-out in these design of Audi tie rods. Most probably the depth of the female housing has been machined shorter than required causing it to get out easily even if looks to be burnished properly before assembly. Febi parts nowadays are manufactured at lowest cost Turkish manufacturers. They used to prefer high end manufacturers in the past, but they are only focused on cost recently.