POST should check that HSE clock is running and not internal 16MHZ (HSE fail over). Check RCC_CR bit 0 (HSION). Should =0 is if running off HSE or LSE clock? Maybe this should be accessible by CLI?
Verify HSE and LSE clock frequency. Refer to STM32F411 reference manual 6.2.11 Internal/external clock measurement using TIM5/TIM11. Maybe this should be accessible by CLI?