Kubuntu Linux 13.04 64bit, AMD Radeon HD 4670 graphics
Broken: tested in 2.70 official release (2014-03-19, hash 19e627c), 2.68a, 2.61
Short description of error
"Offset" option (as I think) means that Copy Rotation Constraint
permits user rotating that bone. But this not always the case.
When Copy Rotation Constraint has partial (not 0 and not 1) influence,
constraint options "Invert" and "Offset" conflicts with each other -
causes two bad effects: unachievable angles
and flipping direction of rotation.
Exact steps for others to reproduce the error
See attached *.blend file (this text is dublicated in blend-file).
Bug 1. Bone has vast "dead", not achievable ranges. Try rotating
the Blue bone by R->X->X - it is impossible to make
bone travel full circle.
For comparison, try to make the same with the Green bone -
that is okay and easily makes full circle. The only difference
between them is flag "Invert" in constraint.
The Red bone even almost "paralyzed" by setup of its
Copy Rotation Constraint: Influence = 0.5.
Bug 2. All bones have the same orientation and roll.
Select Red, Blue And Green Bone. Try rotating them by hitting R->X->X.
Bones rotates in different directions or not rotates at all
depending on Copy Rotation Constraint setup.