Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U575/OTG_FS/GRXFSIZ#0x0
The application can program the RAM size that must be allocated to the Rx FIFO.
RXFD
https://github.com/modm-io/cmsis-svd-stm32