The problem of I2S driver?

[BearPeak]

My project is use I2S to collect camera data,and the idf is esp-idf-v2.0.
But it has some problems.
If camera pclk is 10MHZ,and set i2s clkm_div_num = 2 ,it can normal work.
This is the set i2s mclk code,the camera's pclk was seen with a logic analyzer and is 10MHZ.
I2S0.clkm_conf.clkm_div_a = 1;
I2S0.clkm_conf.clkm_div_b = 0;
I2S0.clkm_conf.clkm_div_num = 2;
But if set camera pclk is 20MHZ,and set i2s clkm_div_num = 1,there are various problems.such as Reset,Print Guru meditation Error ...
This is the set i2s mclk code,the camera's pclk was seen with a logic analyzer and is 20MHZ.
I2S0.clkm_conf.clkm_div_a = 1;
I2S0.clkm_conf.clkm_div_b = 0;
I2S0.clkm_conf.clkm_div_num = 1;

I don't why doubling the rate of both will cause problems？