One other question would be as to how he jacked up the trailer to remove the wheels and pack the bearings? If he was incompetent he might have jacked up under the axles and bent them himself.
That's one of the reasons I do everything I can myself. Some of these shops have inexperienced young people doing these kind of jobs.
BTW, it looks like your backing plates have a 4 bolt pattern, but it may just be how I see it in the picture? I don't remember from my experience if the 4 bolt pattern is square? If so they could be mounted the other way and the axle wrong?