Why does my replacement camera shake back and forth with phone still?

By the time you order the best quality parts you might be close to the price of paying for a somewhat expensive but very high quality Apple repair. Not sure of the camera part but to get the glass, digitizer, home button and related parts from the best quality my cost was going to be over $100 so I decided to pay the $125 Apple repair price....most of the aftermarket iPhone parts will not be high quality. I hate it but that is the reality of the situation.

I would ask for a replacement from iFixit. I agree that you should verify if any adhesive was required to keep the lens in place and thoroughly review any repair guide (I haven't reviewed any guides on this). It sounds like if it is a 'set and go' type of component placement then it is a faulty camera.

I don't remember if this was an iPhone 7 or not, maybe a 6, but I had the same issue. The camera focus part had stuck and just needed a little nudge and then the shaking stopped. Perhaps that will solve it for you.