Were those -2dB at 10kHz and -3dB at 15kHz readings through the Eros, or through the stock electronics? Were they exactly the same on both channels?
If the measurement was through the stock electronics, and/or if the rolloff is different between channels the playback head is probably worn and needs, at the very least, a relap.
If the rolloff was measured through the Eros, the next question is how long and what kind of cables are between the Technics and the Eros? Some cables can really roll off the top end, so even if the measurements were taken with the Eros it could still be a worn head or it could possibly be incompatible cables*.
The Eros was tested on a known good deck here and the response was flat, so it's reasonably unlikely that anything other than the wrong EQ switch setting would make the Eros responsible for the rolloff. You could send it back and we could test it, but without the actual deck and cables you are using it would be impossible to say exactly what the issue is.
* I will note here that "incompatability" has nothing to do with the price or reputation of the cable used. It all boils down to cable capacitance, which varies with brand and model, and always increases with length. In general you want the lowest capacitance possible. Short cables (like 1/2M) are always a good bet, and a cable with something less than 20pF/ft capacitance is a good bet.