What are the problems; the doors don't work properly or the finished job looks bad?
What is the experience base in your company for this type of work?
Where are you getting your 'technicians' from? How much experience do they have in construction and installation before you send them out to solo?
One observation of mine is that installers are often urged to do the job quickly so they can get on to the next customer, thus leaving it looking like some hack was there rather than a professional.