GFI tripping when plugging in to charge batteries

I also own a GD 21G that will trip any ground fault plug that I plug into. From reading on the Grand Design Forum it seems that every GD with an installed generator has this same problem. One member reported that GD told him the problem was that the neutrals for the RV and the generator were bonded together at the generator transfer switch causing the problem and gave him a fix. I will not try to restate that fix here. The fix should come from GD and be done by dealer / service tech.