Whenever I start the game, I can use a ps4 controller via usb just fine, everything works out of the box. But it'll stop responding and switch to keyboard controls randomly after loading a section

I got a bad and a good news for you and other people with this probleme...

The bad the game, BG:DA1 may "lost" your controller when you load a save, on some cinematics/cutscene, after some return on menu or loading some sections.

The only way to deal with that is unplug/replug your controller, i never see any patch for this.

The good news now: this is bug never, really never happen on BG:DA2. \o/