Vector 3 Torque effectiveness incorrect reading

I did some torque efficiency training last week and I found there is an issue of reading on Edge 520.

When I pedal with just left leg (uncleat right leg), torque effectiveness shown : 99%(Left) - 55%(Right);

and when I pedel just with right leg (Left leg uncleat), torque effectiveness shown : 99%(Left) - 99%(Right).

Clearly this is incorrect, because i dont pedal on left side at all, pedal spin smoothly without stuck at left side

Beside than reset them, does it possible to determine this is hardware issue or software bug?

I did update both edge 520 & vector 3 to latest firmware.

Thanks.