Gender switch between West and North Germanic

I was just looking at regna- (in Torp), and it seems to be (only) masculine in West Germanic languages and (only) neuter in Gothic and Old Norse. I seem to have run into a lot of the same (masculine in W.Gmc., neuter in ON.), although I can’t remember them at the moment. Is this a well known development? Presumably, most of these words had a single form and gender in (early) Proto-Germanic; can this be reconstructed? I do dislike having a lot of splits for basic words, as it simply doesn’t seem plausible.

There are quite a few words like that, but I haven't found any explanation for it. It's possible that both genders existed side by side in Proto-Germanic?

Yes, but what is the original gender? Why did a change occur, why some words and not others, i.e. what qualities (in form or semantics) do they share? And, if they did coexist, why are they so clearly polarized between groups?

(No pressure) ;) Seriously, I often wish I could just peek back in time and just listen to how these languages really were. Reconstructing from such incomplete data is a pain.

Maybe there was no original gender. Many modern languages have productive processes of word derivation that are not specific to gender. For example, Dutch -schap can be both feminine and neuter, and different words that are derived with it have different genders. gemeenschap is feminine gender while gereedschap is neuter.