I just leveled up and got this crew member with 0-0 explosive damage.
Not sure what is happening - I just updated to 0.840.

There wasn't anything notable happening to point out.
Screenshot

Edit: the screenshot was not uploaded for some reason, uploaded now.
Additionally - the same skill on the skill tree (which I simply hadn't noticed before since it was useless in my opinion) had the exact same issue.
So since I cannot change the post title - it is not a crew-skill bug, it is the skill itself that might be bugged.