So I've had a bit of an issue with ships spontaneously blowing up while playing as the Hiigarans.

First was a 2v1 match with a CPU ally. I built up a big fleet, full of various BattleCapitals including 6-8 destroyers. Out of nowhere, my CPU ally surrenders. That exact moment, all but two of my destroyers simultaneously explode right in the middle of the fleet. No enemy units in the area, no shots being fired.

In a different match, I have 4 Marine Frigates flying around to capture debris and unique map objects. I have all 4 trying to sieze the Foundry object on Hyperproduction, and they're mostly done with the capture process when 4 enemy Infiltrator Frigates show up and start capturing nearby debris. I accidentally order my frigates to capture the enemy frigates when trying to click on them. Immediately, two of my marine frigates explode upon lifting off from the Foundry. I run with it and send my remaining frigates to board the infiltrators.

They successfully carry out their boarding. Except one of the captured frigates explodes the moment it would come under my control. I take the other captured ship and send it away. I take my two remaining Marine Frigates and board the last two Infiltrators. As before, both captures succeed. Only this time, it's one of my own Marine Firgates that explodes upon succeeding in the capture.

So I started with 4 Marine Frigates, ended up with 1 Marine Frigate and 2 Infiltrator Frigates. I was not running over the frigate limit, and these ships were not taking any fire.