Yeah, so for some reason the spiderbots end up trapping themselves by building on top of their own legs. To address that and get them unstuck, the mod tries to make them jump out of the way (it turns the spiderbot into a projectile and launches it in a random direction to a non-colliding position).
There are a couple other scenarios where they turn into projectiles, namely if they get too far away from the player (i.e. you get in a train and go far away, they'll launch over to you when you get out). But I'm assuming you're talking about when they're building.
I know it's pretty derpy and janky, so for the next release I've been working on a better "smart-jump" for them, where they jump in the direction they're looking, and only jump the minimum distance to find a non-colliding position.
I'm really glad to hear you're enjoying the mod :) Let me know if the throwing you mentioned is different from what I've described here.
p.s. a little more context in this thread: https://mods.factorio.com/mod/spiderbots/discussion/6728f7acc2c60bb5949dc13b
