DW1000 blocking level

Hello all,
I have been testing RF performance of the DW1000 using the EVK1000, particularly its receiver capabilities. In the datasheet in Table 5: DW1000 Receiver AC Characteristics, it is stated that the in-band blocking level is 30dBc (hence, in case of receiver sensitivity of -102dBm in 110kbps datarate, an in-band CW interferer of -102+3+30 = -69dBm would cause the sensitivity to degrade in 3dB, resulting in 1% per at -99dBm input UWB signal). However, from my testing, an in-band interferer CW with power of -88dBm has caused 3dB degradation in sensitivity - resulting in blocking level of 11dBc only (19 dB worse than stated in the datasheet). I was testing the DW1000 in ch5 while the CW interferer was injected using a reliable signal generator. also all the cables were calibrated using a SA an the DUT was placed inside an RF cage to prevent additional MMN.
How this can be explained?