I'm posting this in case someone else runs into the same problem.
Had an issue when the fingers had collapsed in on themselves when adding the bone constraints. I don't know how, but the 'Original Length' value of the Stretch To constraint on the MCH-Fingers was higher than default. It doesn't look like it can be 0, but I set it as low as it will let me, which fixed the problem.
Hi Jake,
you just need to press the little x button on the right of where you have circled.
This will reset the value to be what it is meant to be.
This can happen if you add the constraint when things are not at their rest position, or if you add the constraint and then move things is edit mode.
That button will sort you out but you must go in the order of the hierarchy or you will introduce a stretching error down the chain.
So start at _01 the _02 and _03 etc.
(don't do _03 then _02 then _01 as you will just make it worse)
Hope that helps.
Hey Sheila,
This happens anytime you change the length of the bone in edit mode after you have already added a stretch-to constraint.
Sometimes it can be really obvious - as the problem can get exacerbated the further down the hierarchy it goes.
But sometimes it can be really small and be just enough to cause you to scratch your head for a really long time.
The key to to remember that this can happen when you move things in edit mode.
Of course, it wasn't an issue in the demo I made for you the other week where I rotated the whole arm. I won't tell you why but I will ask you to think about the reason.
(hint: Read this whole comment again from the start if it doesn't jump out at you)