Yes, there seems to be a number of issues with viewers that I don't understand completely. I've asked a few people who create current gribs for help but no one has pointed out a problem.
For example compare your results to firstname.lastname@example.org
and put this in the body (this current model has limited coverage--not world-wide):
It doesn't work on zyGrib and perhaps a few others. Most sailors where internet
access is limited will be using airmail and viewfax which work.
I haven't been able to find a real difference in viewers. I could put the current on a wind
layer instead of trying to use the correct GRIB definitions for current. I suspect this might be part of the problem. But I don't know for sure.