Can under eye bags come back 1 yr 1/2 after lower eyelid blepharoplasty? (photos)

If these are your post-op photos clearly a revision is required. Fat transfer sounds great in theory but often enough the transfer does not persist. I think an external incision approach now would be best and the incision heals very well and it allows any necessary skin and muscle trim as well as fat removal. You have a correctable problem. Your surgeon should be willing to perform the revision 

It is unusual for the fat to move after it has been repositioned if done correctly.  Sometimes some fat should have also been removed if you had a large amount of fat.  In those cases it can stay a little puffy.  But if you looked good for awhile and only now have fat pads, - that is unusual.  You will need some sort of revision.  See an oculoplastic surgeon who can help determine what would be best for you.    

A detailed examination is in order to determine if the fullness that we see in the photos is actually caused by herniated orbital fat.  You can do you own test actually.  Put your finger on top of the lower eyelid fullness.  If this is hard, it is likely that the fullness is actually the contour of the orbital rim.  The fix really needs to be anatomically based on just what surgeons normally do.  It is interesting how little has changed from your preoperative photos.  In comparing the current pictures with your before images, you still have under eye filler that makes you look irregular.  I personally suspect that a fussy filler service might actually take care of your lower eye issues without the need for surgery.  Your upper eyelids look like they have become heavy since surgery.  Do you think that might be the case?  Generally, since you went to the trouble of traveling out to California for surgery, I would encourage you to see your original surgeon to be assessed and see what they recommend.  That person should be highly motivated to address your concerns.

Yes that is unusual but not toally unexpected.  It is why I am not a big fan of fat transposition  especially through the transconjunctival approach.    With  fat transposition there is no effective scarring of the orbital  septum which acts to secure the infraorbital fat inside of the orbit.  You may need a repeat procedure unfortunately .

The fat repositioning procedure you had is often unsuccessful.  For a short time the fat stays where it has been repositioned (below the muscle at the bony rim below the eye) but it can loosen and return to it's original position.  A fat repositioning procedure is reserved for individuals that have a prominent tear trough but you would be better served, in my opinion, with the standard transconjunctival fat removal Blepharoplasty. This is what you need now which will permanently eliminate the under eye bags.