2 - overstimulation
https://archiveofourown.org/works/93648191/chapters/250170581
"I-" his voice. The most familiar part of his body. It was there on the Hail Mary, now it's here in his throat as his own human song. But it's still one voice trapped by one narrow throat, and it strains uncomfortably as he tries to keep speaking. "Yes. Much to understand. Parse. Very new. Exciting!" Terrifying. Science, like space travel and space ship maintenance, usually is.
"I bet." Grace's fingers tense, plying into the fat and muscles under Rocky’s carapace. Ah, no, his skin. Thin and fragile and easy to pinch. He doesn't like using his own fingers to squeeze it, but it's good when Grace does it. That makes Rocky warmer. Warmer doesn't make his shivering stop.
"You're still sure about this? If it's too much we can stop any time." Grace asks.