When I installed WB's I greased everything up before assembing them. Then, the next year I tried to pump grease in. Half of them were no go.
I let it go a year and then tried again and still couldn't get half of them to take grease.
So I took the offending wet bolts out and tried to pump grese through them. Still no go.
I removed the zerks and found that they had only been drilled enough to get the zerks in! They had holes in the other end but they weren't drilled all the way through! By this time it had been too long to get any satisfaction from eTrailer so I ordered more and fixed it without any further problems.
Moral of the story; grease them right away and make sure our off-shore partners and doing their usual thing!