I was trying to figure out my stamina issues in the ‘tips & tricks’ thread and eventually realized the cause.
If you have high enough speed even butchering and walking will make you out of breath since you are able to execute multiple stamina draining actions per turn but stamina regenerates on a per turn basis.
Currently playing on build 10613 to let the nested container stuff get a bit more stable but it was the same on older versions as well.
You can replicate it without any mods, merely the traits quick and fleet footed with some 20-30 mouth encumbrance is enough. If you boost your speed further with mutations or through other means to ~140+ you will lose stamina from walking even at 0 mouth encumbrance.
I’d make a github bug report but they’ve yet to send me a confirmation e-mail to complete my registration and I can’t be bothered to make more accounts.