What ADC are you using? Normally those I2S series termination resistors are 10-150 ohms. The need for higher resistors indicates that your I2S signals have issues. Also problems with higher sample rates is another indication of the same issue.
BTW a later version of I2S input FW for STM32F723 can be found here:
https://www.diyaudio.com/community/threads/diy-adcs.419922/post-7887758
BTW a later version of I2S input FW for STM32F723 can be found here:
https://www.diyaudio.com/community/threads/diy-adcs.419922/post-7887758