Can't shake the Tommies!

[Tabris]

Originally Posted by Plingus

I was chased for 12 hours by a destroyer that had somehow caught on fire.

Burning escorts is a classic, well-known bug, alternately frustrating or hilarious depending on how immersed you are in the simulation. I've seen it in multiple mods, and it probably happens in vanilla too. I can't speak on it too authoritatively, but my understanding is that it can happen to any small ship that's damaged by heavy seas. If large enough waves swamp the ship, it takes flooding damage, which is why it generally happens to only small escorts and little steamers.

Chalk it up to the enemy's poor seamanship

There are other similar ship self-destruct issues you'll run into. Don't be too surprised if that troublesome 20k ton "Modern Passenger Liner" spontaneously scuttles itself, which can even happen in calm seas. Sometimes subchasers and armed trawlers can spectacularly blow themselves up with their own bombs, if they're trying to hit a target at a shallow depth, since their top speed is lower than that of an ocean-going escort.

Welcome to the party btw!

[Hooston]

The waves can be a bit too destructive in many mods. Flower Class corvettes are particularly vulnerable, when IRL they were horribly uncomfortable but also very seaworthy. I've found that it is helpful to look at the wave height settings in SH3 Commander and set the waves to be as small as possible.
GWX includes Uboats in some convoys that will attack as soon as the convoy spawns (around 30km away). Given the stupidity of the SH3 AI these boats often attack on the surface with their deck guns, even in daylight, leading to masses of wild firing from all sides that damages many ships. All this usually occurs out of sight of your boat and is over by the time you arrive.
OneAlex seems to be very keen on air attacks on convoys. An air attack leads to lots of damage, both from the aircraft and from stray rounds as above.
It's all a bit mad; best not to use the external view and just pretend that there's some more rational explanation.