legged robot fly away when applied torque on leg motors

[orange_juice]

You can see in this link.
https://youtu.be/P5sMrNqqpzk

Script output:
QP solution: x = [1.97274706e-02 3.30290196e-01 1.20748465e-12 1.97274709e-02
3.29880345e-01 1.20957151e-12 1.97274712e-02 3.29470003e-01
1.21165332e-12 1.71003468e-02 3.29470003e-01 1.25240257e-12
1.71003468e-02 3.29880345e-01 1.25050645e-12 1.71003468e-02
3.30290196e-01 1.24860524e-12]
torques= [-0.007089229708272171, -0.11855267506778587, -0.08752904921373267, -0.00708923078590513, -0.11840497984810472, -0.08742045564322172, -0.007089233043473016, -0.11825713974426294, -0.08731173018363321, -0.0061475401180276276, 0.11823816253825556, 0.08731064634188268, -0.00614754038323656, 0.11838597957260431, 0.08741937000552441, -0.006147540646661376, 0.11853362213019486, 0.08752796377193674]

The QP solution x is the contact force return by a qpsolver.
Torques are calculated using the jacobian matrix.
Torques only applied once, and it seems to be very small, but the robot just fly away and never fall down.
I wonder what the cause of this problem. Can any one help me? Thanks in advance!

Here is the code:
https://github.com/uyiyiyi/hexapod