Just a wild guess, but I imagine the shop drove in the inner bearing stops without checking bearing "stick out" before pressing the bearings on the axles.
You have to install the inner metal stops first, then dry fit the bearing, see how far the bearing sticks out the end of the axle housing. If the bearing sticks out too far, you are supposed to remove the inner bearing stop piece, and machine it down to obtain the correct bearing stick out.
If you don't do this, and the bearing sticks out too far, when you slide the axle in and bolt the brake backing plate/axle seal plate down, they will "bow", and leak.
I personally think the "bearing stick out" they call for is a little much. You want a little "stick out" to put a bit of pre-load on the bearings. But, to much stick out will cause bent brake backing plates
If the "stick out" isn't an obscene amount, I always though that maybe you could install some original two piece axle shims between the axle tube end and the brake backing plate to get the correct/less "stick out". This would be easier then machining down the bearing stop parts that are drove into the axle tube ends