OK. So, here’s the deal. I downloaded the manual for that heli and it’s supposed to be leading edge control. You assembled the head wrong. The blade grips have to be rotated 180 degrees.
Let’s go over this, and this will be kinda long 
First and foremost, in today’s FBL systems where the delta angle is zero, leading and trailing edge control are exactly the same. In other words, there are no advantages or disadvantages.
When you have a rotor head system that has a non-zero delta angle, there are clear pros and cons. To start off, what’s delta angle?
Look down on your heli’s head with the grips at zero pitch. Draw a line between the two grip balls on a two-blade head and a line perpendicular to the blades and through the center of the head (like a virtual flybar). The angle between these two lines is a measure of the delta or delta-3 angle.
Think about a typical heli head. It’s what we refer to as semi-rigid because the feathering shaft and blade grips can actually teeter in the head block due to the compliance of the damper material. Helicopter rotor systems are designed to flap to compensate for the di-symmetry of lift in forward flight.
Simply put, the advancing (left blade in a CW rotating system) blade sees a higher-speed air flow due to the blade speed plus the heli forward speed while the retreating (right) blade sees a lower-speed air flow.
The result is higher lift on the left side of the rotor disk and a tendency for the heli to pitch up as a result (remember gyroscopic precession says that the resulting action on a rotating body occurs 90 degrees from the point of application of the force).
When the blades are allowed to flap, the advancing (left) blade sees more lift and flaps up, which reduces its relative angle of attack, thus reducing lift. The opposite occurs with the retreating (right) blade and the result is a more balanced lift distribution across the rotor disk.
Ok, back to delta angle…
When the blade flaps, the blade grip moves up or down with it, but the ball is constrained by the link that is rigidly attached to the swashplate. So, where that ball is located with respect to the teetering point or center of rotation of the feathering shaft dictates how the pitch of the blade varies during flapping.
If the ball is located at the teetering point, then the pitch does not vary with flapping. However, if the ball is shorter (i.e. non-zero delta angle), then when the blade flaps the pitch will increase or decrease depending on the flapping direction and whether it’s leading or trailing edge control.
Leading-edge control with non-zero delta angle will cause a decrease (increase) in blade pitch with an upward (downward) flap…this causes a natural restoring force that tends to reduce the lift on the blade. This is referred to as correcting or positive delta.
Trailing-edge control has the opposite effect…a non-zero delta angle will cause an increase (decrease) in blade pitch with an upward (downward) flap…this causes an increase in lift, which can cause an instability and lead to blade fluttering in extreme cases, but in general will only increase the stability of the heli. Of course, this effect can be partially reduced by stiffer dampers, but only to a certain extent. This is referred to as uncorrecting or negative delta.
In general, for quick handling you tend to want to run stiffer dampers to reduce the amount of flapping because this allows for a more direct transfer of disk forces to the heli airframe and results in a more responsive feel. Beginners would prefer more flapping (softer dampers) because it has a stabilizing effect.
Your three-blade head looks like a rigid design - no dampers. But because it’s DFC the phase angle will be WAY off. The blade will be late in the cycle. So don’t change the firmware - take a closer look at your manual and especially where you are building the head. Flip those blade grips over to make it leading edge control and then it will work.
