Bliniking shadow on rendering result I am making walking robot and get a weird blinking shadow on the robot's body.
This shadow lasts only one frame and then disappears.

Blender: 2.77
Renderer: BI 





Frame 3 is similar to 1st (without shadow).

If any details help to fix this just ask. 
I don't know what information might be useful for it.

Response to Sonace:

It doesn't help.



And the robot doesn't have any duplicates under its body.
Well since nothing works im posting something that may work. sellect the object you have this problem apply a smooth shader in it and then add a subdivision modifier change it to simple from catmull-clark.Then change subdivisions to something big like 4-5.
And check again to see if it works.If this still doesnt work add one more subdivision modifier but not simple this time.And check again.
This wont work for sure*