Only other solution I can see at the moment is having to create hyper specific animation profiles. Which would be super time consuming and hard be fully accurate with I think.
I'm entirely open to being proven wrong in any case. My experience with creatures/monsters in Skyrim modding is entirely limited to the superficial points I needed to make it work with SexLab. I'm by no means an expert here.
it does not need to be "hyper specific" (unless your talking about mudcrabs or dragonborn spiders), just separating the "ChaurusReaperRace" from the "ChaurusRace" would be helpful, because by the looks of it most of the Chaurus animations that have been made so far are for a setscale 1 Chaurus (the Chaurus Reaper), but the "normal" Chaurus is setscale 0.65 so there animations are not truly cross compatible.
i think the reason why it "seems to randomize it for some" is because there is a third setscale/height control in the world editor (the first 2 are in "race" and "actor")
turning off "even actor heights" for the AshHoppers could be helpful, but only if it stays on for the player/humanoid npc, and only if the animation playing was made for a setscale 0.5 AshHopper.
SexLab already gets that specific as is. While race specific adjustments option is enabled, which it is by default, any changes you make in specifically aligning animations for ChgaurusReaperRace will be stored and reused entirely separate from the adjustments you might make for "ChaurusRace." When I say hyper specific profiles, this is what I mean - it's unrealistic to expect SexLab as a framework to go so deep as to create a fine tuned alignment profile on a per creature race basis. It's the same problem with human on human animations, any default alignment profiles I create beyond the initial "generally works" alignments... There are different humanoid skeletons and bodies, making their half of the equation useless to fuss over here, and there are also creature mods that make relevant changes that would have to be dealt with.
When you use race specific adjustment profiles, and spend the time to get them done right, you shouldn't ever have to fuss over alignment more than once per animation.
Skyrim's handling of some creatures is to unpredictable, and until there's a solution made known that spans different races within the same "creature type" in a reliable way, there is nothing reliable I can do about it.