Is there a secret trick for installing axle shafts?

Converting my 8.75 rear to big bolt axles from Dr Diff and I can't get them to go in all the way.

They start to go in and stop with about 3/8" to go, I tried turning them a little bit and pushing (also turning them a lot)...but no luck. I can get the nuts started on the housing bolts but I really don't want to crank on those babies too hard and damage anything.

I also tried to put my original axles back in for the fun of it and I have the same results...they don't go in the all the way.

I eventually go the driver side to go in (both new and old axles) with a couple taps of the hammer, but the passenger side has no interest in playing nice.

What gives?

What am I missing.

Thanks in advance.

Paul