Hard to read the picture. I guess loose bearings, under inflated, out
of balance. Have you checked the toe in and camber on the trailer?
Drive straight with trailer, stop and measure toe in and camber when
the motorcycle is on the trailer. Some of those teeny tiny tires are
not rated for very fast speeds. I had to replace an axle on my trailer
after a spinout. But this was a 3,500 pound axle, not a teeny tiny
axle/tire combination. It may be that the rating of the axle was
optimistic/unrealistic and did not handle the load or a bump once.
Overloaded like in a turn and hitting a bump could have bent the axle
causing permanent excessive camber which can eat up tires.

http://tinyurl.com/34w29g

One of the folding 4' x8' kit trailers.   It had several
trips from S. Calif to Salt Lake City loaded to the gills
without this kind of wear.

Recently, been towing a honda CBR1000, about 475lbs.  3-4
thousand miles.  Major wear on tires.  ONLY change was
installation of oil filled hubs.

??????

thanks

gary