Hey guys!
I have just started using mGear, and I have noticed that when I create leg rigging and switch between IK and FK, the toe bone will offset. I have seen some discussions about this issue on the forums, but it seems that a definitive solution has not been found. 
for example:
http://forum.mgear-framework.com/t/foot-l0-0-jnt-rotation-ik-fk-diffenrent/1900
http://forum.mgear-framework.com/t/switching-from-ik-to-fk-is-adding-rotation/3295
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I noticed the default guide template also have this same issue(Slightly by default)
Here is my mGear Test Rig
I tested for a while and found that I have to ensure that foot_L0_0_loc, foot_L0_1_loc, foot_L0_2_loc are aligned in a straight line to prevent offseting…(However, it is evident that the ankle, ball, toe of the character model cannot be aligned in a straight line ) .
For my test rig guide’s foot_L0_0_loc, foot_L0_1_loc, foot_L0_2_loc are not in a straght line, but in the same rotate plane, So I am wondering what is the cause of this issue? and how can i fix this？ and how should i work with the (leg_2jnt_01+foot_bk_01)?
Thanks!
Houdinini