The proper vertices have been weighted 1.00 to the one bone, they aren't weighted to any other bone. The other toe bone, identical, works just fine. There's only one Armature modifier attached to the character. I've checked, the IK and copy rotation constraint does not affect the bone in this way. And yet they behave like they are 0.5 weighted. I've tried duplicating the bone several times and simultaneously weighting the vertices to each bone to make it move quicker and not even that works.
Here is a link to the file: https://files.fm/u/at43v96p?k=a36b860b