Problem receiving with libusrp2 in decimation 4

GNU Radio
1

I’m using libusrp2 with c++ code.
I call usrp2::make, set_rx_decim, set_rx_gain, set_rx_center_frequency,
and then rx_samples in a while loop
when I use decim 8 it works fine. but when I use decim 4 my handler
doesn’t get called.
any ideas?