Our Interphase unit died....well the transducer did, and we couldn't get one so I installed a B&G Vulcan 7 with ForwardScan in its place.
The ForwardScan is very susceptible to boat movement, I think this is what leads to the "false images" . It seems to work well in calm water and at low speed. If there is any up and down  movement of the boat, the image will not be useful as the device can't compensate for that.
Cheers
Alan
Elyse SM437