In the TDSHT3+ my Eye diagram fails at Top and Bottom mask+ but the Overshoot and Undershoot measurement pass. Why is this happening?

In the TDSHT3+ my Eye diagram fails at Top and Bottom mask+ but the Overshoot and Undershoot measurement pass. Why is this happening?

Due to the Oscilloscope’s limited digitizing levels, the eye diagram gets low resolution; this may lead to overshoot violation in the eye diagram. Optimal algorithms are used in Overshoot and Undershoot measurements, which leads to more accurate results than the eye diagram measurements. So it is recommended to analyze the eye diagram.