Okay, I've been trying to figure this out for a day, and it's nearly made me drop the mod. When I start with my sister she is always crawling and I can't seem to figure out how to change it. Her breasts are small, I didn't restrain her in anyway and I'm not even sure what the mod means by "rules" regarding movement, as I can't find anything like this. The only document explaining the mod in the library is the sexuality scale. Any help would be appreciated at this point. Is this a bug?
Edited: 
Viewing post in Aric's Expansion Rebred
The only other mod I have is the default one and the random portraits. By console you mean the box that opens with the game, yes? Nothing unusual pops up there. I reinstalled the mod and went through the instructs piece by piece. Even reinstalled strive. Nothing. Still get the same bug. Seems to happen with every starting person except the stranger.
Constants killed the radio star. The very top error shows that Constants has an incompatible type.
Try disabling Constants and trying again, I would almost bet that'll resolve it
Edit: This should fix that - https://itch.io/post/1488530
Unfortunately, I already had the mod turned off by now as I was testing. At first, changing the value gave me an error, but it did get rid of the constants errors. Sadly, it seems my girl is still crawling. T.T
It's very difficult for me to test as sometimes they walk, sometimes they crawl for now reason. I began this game with my girl walking, but now, on day 5 she's suddenly begun to crawl again. I wonder if portraits could be causing this by any chance? Is that a long shot?
Edit: Then, I might have to restart my save again for it to work. I'll try that. @.@ Rip.
The factors for checking why she may be crawling are these:
Is she wearing cuffs/restrained (equipped via the inventory)?
Is she set to “permanently crawl” (via slave rules)?
Is she swollen/pregnant/cumfilled (checked on the bottom left panel of Statistics)?
And finally, is her energy bottomed out? (Main page or slave page, fixed via spell or sleeping)