My assumption is that this had previously worked fine, now something has changed making this problematic.
Start w/ the basics.
Has anything changed, like a new 1.21 Jigawatt stereo or other electronics added between working fine and having issues?
Monitor the voltage supplying power to the instrument, including during the problem. At the instrument measure +12V to ground. It should be reasonably constant.
Do a light tug test on the transducer connections to verify solid retention. Disconnect the transducer and perform a visual inspection of the transducer wires. Verify that all wire strands are intact and not corroded.
Do a visual inspection of the cable over the entire length. Verify that the cable is not cut, crushed or kinked.
The cable should be at least 1m from VHF + SSB cables. The cable should be at least 2m from the ±20² radar beam.
Has the surface of the transducer been verified to be free of marine growth or other damage? Mine may be removed from the engine room and replaced w/ a dummy plug. I use the two hand method, to yank / replace w/ one hand while covering / exposing the hole near the keel w/ the other hand.