The force on torsional spring doesn't add up?

[pkucc]

from the please_find_lagrangnian_force_on_eulerian_grid.py, from line 821-864 is below
id_1 = pts_1[ii] # 1ST Node index
id_2 = pts_2[ii] # (MIDDLE) 2nd Node index -> index that gets force applied to it!
id_3 = pts_3[ii] # 3RD Node index
k_Beam = K_Vec[ii] # Beam stiffness of i-th spring
C = C_Vec[ii] # Curvature of the beam between these three nodes

    Xp = xLag[id_1]          # xPt of 1ST Node Pt. in beam
    Xq = xLag[id_2]          # xPt of 2ND (MIDDLE) Node Pt. in beam
    Xr = xLag[id_3]          # xPt of 3RD Node Pt. in beam

    Yp = yLag[id_1]          # yPt of 1ST Node Pt. in beam
    Yq = yLag[id_2]          # yPt of 2ND (MIDDLE) Node Pt. in beam
    Yr = yLag[id_3]          # yPt of 3RD Node Pt. in beam

    # Checks if Lag. Pts. have passed through the boundary and translates appropriately
    Xp,Xq,Xr = check_If_Beam_Points_Pass_Through_Boundary(ds,Lx,Xp,Xq,Xr)
    Yp,Yq,Yr = check_If_Beam_Points_Pass_Through_Boundary(ds,Ly,Yp,Yq,Yr)

    # Compute Cross-Product
    cross_prod = (Xr-Xq)*(Yq-Yp) - (Yr-Yq)*(Xq-Xp)

    # FORCES FOR LEFT NODE
    bF_x_L = -k_Beam * ( cross_prod - C ) * ( Yr-Yq )
    bF_y_L =  k_Beam * ( cross_prod - C ) * ( Xr-Xq )

    # FORCES FOR MIDDLE NODE
    bF_x_M =  k_Beam * ( cross_prod - C ) * (  (Yq-Yp) + (Yr-Yq) )
    bF_y_M = -k_Beam * ( cross_prod - C ) * (  (Xr-Xq) + (Xq-Xp) )

    # FORCES FOR RIGHT NODE
    bF_x_R = -k_Beam * ( cross_prod - C ) * ( Yq-Yp )
    bF_y_R =  k_Beam * ( cross_prod - C ) * ( Xq-Xp )

    fx[id_1] -= bF_x_L  # Sum total forces for left node,
                                 # in x-direction (this is LEFT node for this beam)
    fy[id_1] -= bF_y_L  # Sum total forces for left node, 
                                 # in y-direction (this is LEFT node for this beam)
    fx[id_2] += bF_x_M  # Sum total forces for middle node,
                                 # in x-direction (this is MIDDLE node for this beam)
    fy[id_2] += bF_y_M  # Sum total forces for middle node, 
                                 # in y-direction (this is MIDDLE node for this beam)
    fx[id_3] -= bF_x_R  # Sum total forces for right node,
                                 # in x-direction (this is RIGHT node for this beam)
    fy[id_3] -= bF_y_R  # Sum total forces for right node, 
                                 # in y-direction (this is RIGHT node for this beam)

it can be seen that bF_x_L + bF_x_M + bF_x_R=0, but it then adds the force to node as -bF_x_L, bF_x_M, -bF_x_R ?
The TOTAL force to add on the three nodes should be zero, but it doesn't here, is it a bug?