I concur.
It is not impossible that there IS water in that pack, but when we were in business, all code 37 we found where false-positives to the point we ended hiding it until we could solve the sensor issue.
Iirc, one thing that we saw with cheap generators (usually not Hondas but it could happen I guess) was that there was either no ground, or it would not be fastened properly and that would throw faults/prevent the GFCI from resetting.