Rotor assembly not fitting all the way back onto spindle ?
 

New rear bearing fits all the way onto trailer spindle......rear seal fits over all the way onto spindle....BUT with rear seal tapped in.....the rotor won't go all the way back onto the spindle.

Maybe I tapped the race wrong ? Thought done correctly, but maybe I had the thicker side of race facing the wrong way......

Not sure till I pull the last wheel, compare each section, make sure all parts match up and try again.....

OR.....did the new real seal shrink up a bit when tapped in ?
I tried tapping the rotor on with wood block and hammer but it didn't move at all.

Did you put the right berin in the rear?? Some are (not sure your size) say 1/2" front and 3/4 on rear, that won't let it go back on! Size is just exsanple

X2.. That was going to be my comment also. My trailer has larger spindle on the inside so it takes two different bearings on each wheel. You might want to put a caliper on the spindle and make sure that it's the same along all bearing surfaces.

Yup, I figured that out too..........now I kind of get it........