AD2S1205

I use FPGA drive ad2s1205   for testing fault detection delay time . When EXC , SIN, COS ar NC,  the fault detection delay maximum value is not 125us , but 800us ; if the EXC SIN connect  resolver signal , COS NC , the fault detection delay maximum value is about 24ms .

I wonder what the main reason for this phenomenon, and how to judge whether the the Rotary transformer has broken ?