1.. Make sure the Frequency Shift is set at the Factory Preset marker. If 'shifted" it will throw of the Ground Balance and it might be enough to impair performance.
2.. Check the Ground Balance and adjust the internal trimmer, if necessary, which is user-accessible under the US Flag.
Okay, there is a 3rd thing to do. Try a different search coil. If your coil is "out-of-spec" that can also throw things off.
Then, if all else fails, send it to White's in Sweet Home, Oregon for excellent service. A properly working IDX Pro is a definite competitor regardless of make or model.
Monte