None of my trailers have EVER had an outer seal
Don't take this the wrong way, but if you're having this much trouble with bearing buddies , are you sure your bearings are set correctly? Hate to see you trash a set of bearings because the end play is set wrong.
Not taking it the wrong way at all but why would I have a problem with only one side if I did them both the same way? I tightened down the castle nuts all the way to set the bearings and them backed them off until the wheel turned freely. Then put in the cotter pin and next the Bearing Buddy.
However, I will ALWAYS replace the bearing outer races and use the new races that came with the new bearings.I have tried bearing auto greasers of all kind.I prefer to hand pack, knowing that I know what I'm doing and get grease into every nook and cranny of the bearing.Spin the wheel/hub when seating the bearings.Then back off 1/4 turn and insert the cotter pin.
Could you have two different hubs that don’t have the same machined dimensions where you install the buddies? Or maybe the two buddies are not machined the same size. I believe they can be bought in two different sizes.
I wasn't suggesting that incorrect bearing installation was why the cap wouldn't go on. I just meant that installing buddies should be a straight forward process. If you struggled with that, I could see a chance at incorrect bearing adjustment.