Many buyers noticed that in some cases this device degraded video signal quality (in particular contrast and sharpness)
I found out that reason of this defect is resistor R28 which present paralleled on input of the video amplifier. Resistance 22 kohm is too high and therefore appears impedance mismatching between signal source and input of the device. Obviously it’s a manufacturing defect.
For resolving this problem I replaced on the PCB resistor R28 to 82 ohm (it could be in range 75-110 ohm) and now there is no difference between input and output signal quality.