LMK1D1212: Output LVDS clock is deformed

Part Number: LMK1D1212

Input LVDS clock is standard clock as follows.

However the output LVDS clock (pin12/13) is deformed, see unwanted signal in red circle in below picture. Output pin12/13 is terminated with 100-ohm resistor close to LKM1D1212.

What's going wrong?