XM1110 delay in speed measurement

I have currently an XM1110 installed for our application that use GNSS data and other data to make an estimation of the speed even when we loose the GPS data because of a tunnel.

The solution was installed into the target together with a reference that is a high advanced inertial + GNSS system. The objective is to benchmark with the reference.

But I found that the XM1110 speed – and only the speed- is delayed by approximately one second in regards to the other data which are perfectly synchronised with the high-accuracy reference data (lat, long, heading are well synchronised). The data were synchronised through ITOW/UTC.

The comparison with the reference speed data seems to show that there is a filter inside the sierra XM1110 that is causing this delay (in yellow the reference data filtered).

Can someone confirm me that there is a digital filter for speed and if not what can cause this delay.

Thank you for your help in advance!