I don't run the game, but I'm guessing since it doesn't save your speed when saving you loose the modifier and it reloads the default convar stuff
I know that there are two versions of Speed Cripple breakable and unbreakable, but you get them random or there are specific way to get them, I don't know.
We're not really sure why there is two versions of the speedglitch. The breakable one seems to appears more often when you're playing with 30 FPS, at least for me. Otherwise, no idea. Be sure to restart the game if you die trying to get it. And cross your fingers.
Yeah, ragdolling makes it impossible to get speedcripple without restarting the games. Also, it is impossible to get unbreakable speedcripple twice without restarting the game. Getting breakable is fine and you can get unbreakable afterwards. And obtaining breakable or unbreakable is obtained the same way, I would say it's random which one you get.