I hope this will actually show up in Bug Reports this time...
So I've been pretty varying with ship designs every game, but like using past names. So I did a new version of "Boar III" from a previous game and overwrote that saved design. However, when I had built a couple of those vessels and put them in a fleet, instead of a 6 or 7 total in mass driver weapons and some armor, the fleet had 8 in beam weapons plus shields, which I can only assume was a holdover from the overwritten design.
I think it might have been a UI issue because then I tried a battle against a shieldless opponent and I lost pretty badly.