not entirely sure, but maybe some sort of gravity was involved.

The idea is that a mammalian body (or Groot, since he's also affected) can't handle that many jumps. Jumping through the network like that screws with your body

Its odd that Yondu says "mammalian body". Does this mean that this affects mammal-like creatures (including humanoid ones)? Or is that suggesting Yondu, Groot and Rocket are actually mammals? I mean... one could argue that humanoid alien races across the universe might have a common ancestor with humans on Earth (through Celestial shenanigans, or something) and I suspect Rocket has actual Earth raccoon DNA as well. Also begs the question if Howard the Duck would have any problems with these jumps.

Howard the Duck is invincible. Nothing would effect him :p