Ahh yesh, the ole "missed what I was shooting at but I'll take the sink credit anyway" trick... In the "stock" game, if you hit most of the capital ships in the right spot, the game assumes you hit the magazine, in which case, the ship's shells explode and explode until the ship destroys itself. Stock is bad about that with the entire Japanese cruiser line. Even the destroyers are relatively easy to do that with, so long as they stand still for you to aim at 'em thatta way...

(The destroyers do have that super-iron bow though, that seems nearly impregnable.) You can hit them generally around the rearmost forward main gun turret (side shot, of course), towards the main superstructure, and away she goes. If you're using certain versions of some mods, that can happen also. What mods, if any, do you have enabled?