TX2 no display sometimes suddenly and no any rules

We have one Tx2 Board no display suddenly, plug in tha HDMI cable once more,but still not shown.
repeat restart it,sometimes it displays, sometimes doesn’t.And there’s no rule.
I change the cable, minitor and carrier board many times,find it’s following the Tx2.
But when no display the HPD,I2C waves are all right,the serial port log also can’t find difference.
I’m very confused.What’s the reason? Please provide some suggestions or methods.thanks very much!