I70 depth readings not true

In April of this year I installed an I70 System Pack (Wind Depth and Speed) along with an I70 Multi-functional Instrument Display and an ITC5 converter on my sailboat.

The speed and temp readings are good. The depth is not. Sometimes the accurate depth is shown on both Multi-functional Instrument Display and the chart plotter. Sometimes the depth readings bounce everywhere from 0 to high numbers on the Multi-functional Instrument Display. On my chart plotter the reading will be 6554 ft when the Multi-functional Instrument Display reads zero or close to it when we are in 30 feet of water.

I checked and made sure both the Multi-functional Instrument Display and ITC5 have the latest software packages and they do.

Any thoughts?

Langley Gace