Do you have your lid action set to hibernate?
I know on the Framework 13 the audio board which is at the bottom left of the mainboard, so near the ctrl key is where the sensor is used for lid detection. As the Framework 16 does not have this audio board, I’m not sure, but I think that something triggering your lid action, or you accidentally touching the power button are all the most likely way hibernation is just randomly occurring.
Edit: doing a bit of digging, it seems this thread talks about where the lid detection is happening:
How is lid close detected on the FW16? - Framework Laptop 16 - Framework Community
Bottom of the bezel just left of center and is ambient by nature. If you are putting anything there, like a phone or otherwise blocking light this could be triggering it. If you are playing in a dark room, and the screen is VERY bright due to the game, but then black due to loading screens, this might also trigger it. All just theories.