It's possible that it didn't slide into the bracket and instead slid over it (or under). If you look at Sethro's picture above, that's what might be happening with his. It would be visually obvious though. The side of the bumper would stick out (if slid over bracket) or would show a big gap (if slid under).

Interesting, I don't remember any plastic inserts, but I may just have missed them all together.

Adjusting the bumper alignment is actually fairly straightforward if you have ever taken the bumper off. Referring to the photo of the bumper carrier in LPMM's post above (the picture showing the carrier in the red rectangle), you can adjust alignment using a washer or two on the topside of each vertical carrier tube and angle-grind the same thickness off the bottom of each tube. Then slide the bumper back, tighten the 2 long T50 bolts and check alignment. If neccesary repeat using more/ thicker washers. A mm or two will make a big difference to the alignment of the bumper. The hitch I installed had angle-iron carriers so I wasn't able to re-use the plastic inserts from the original round ones. The inserts just act as spacers to prevent play between the T50 bolts and the carrier tube. Getting this right isn't too bad with a helper but it looks so much better.

FWIW, I had the same problem after installing my OE hitch 2-1/2 years ago. I inserted my dropout into the hitch, loosened all the mounting hardware (14 nuts and bolts?), put my floor jack under the dropout and carefully jacked up until it all lined up then tightened everything down.

Unfortunately late last year I took the car in to my dealer for some warranty work, and they pulled the rear bumper to replace a couple of the park sensors and when they put it back on it's now misaligned. When I questioned it I got the same response as many of you- it's not adjustable. When I showed them pics of the properly aligned bumper I'd taken after installing the hitch they said I just got lucky. So of course I had to refit my bumper again. A week later I took it back to the dealer and showed them the correct fitment and the service manager just shrugged his shoulders and said his techs don't get paid enough to do all that extra stuff that the shop manual doesn't cover. I'm now using a different dealer.

I would love if you post a step by step of how you did it.

03 X5...Did my own install of OEM hitch- same result...I even back tracked to see if I missed something-

I'm bumping up this old thread, everywhere I go I get the same "yeah thats just how its supposed to look"

Anyone able to line up the bumper properly??