Okay okay book grace was a pretty easily angered guy- I've seen some people headcanon him as having anger issues- and I just want to say I think itd be really fun to explore this on Erid specifically.
Think about it- Grace has been in a constant state of stress and anxiety for years at this point. From the stress on Stratts vat, to the whole being forced on a suicide mission thing, waking up in space with no memories and two corpses to keep him company, almost dying and losing his only friend up there, then making peace with slowly starving to death to save his friend-
Grace was constantly stressed and scared and anxious over something. There was always something to worry about. So when they get to erid and the eridians make sure he's safe and healthy- making a living space for him where he can live happily, making him food that won't kill him, letting him teach again-
I think after reaching Erid, when Grace finally doesn't have to worry about dying or saving earth- all of that stress and trauma just finally catches up to him.
I think itd be really interesting if Graces response to that trauma was anger. Getting angry at the eridians for asking questions when something should be obvious, snapping at people for the stupidest things, getting treated like a zoo animal- he's an alien here, he knows that, but I also think itd be really interesting to explore if his temper and anger issues made themselves known on erid again.
Just. Grace struggling with a lot of trauma and issues that turn into anger.