ADuM3481 multichannel SPI interface application issue

Dear Sir,

We used isolated supply for each one and ADuM3481 for isolate SPI lines, from main CPU all 2 ADC's are sharing same DIN, DOUT, Clock lines and separate CS, When U602 and U605 both on board the SPI communication is failed (As attached waveform, CH2 is SDI1_MCU (VOD)). Removed which one, the other one on the normal communication.

Schematic as attached file.

Please help me how to solve this issue. Thanks!