SPI bus mistic signal problem

I have a “mistic” problrm witdh 2686/87 SPI bus . I continously read from the bus (ADC) and i look on signals a problem . Some times the CS signal interted . In my app in normal The CS signal inited HIGH rest state , Active low . But some time time under run the state is inverted :slight_smile: , and some time after is back .

I dont do reinit . What is the proble …