Sorry to bother you, the problem is not esp32. I didn’t work much with DDS generators, and this is their typical drawback. The topic can be deleted.
Thank you.

I need to generate a sinusoidal signal and digitize it with an external ADC. The generated frequency and digitization must be strictly synchronous, so I took the ADS1256. It is supposed to use the 8-10 MHz frequency from esp32. If the generator and ADC are operated from a separate frequency source, ...