The stm32 datasheet says that the number of wait states for reading the FLASH memory have to be configured based on the voltage used to power the microcontroller, and frequency. When running at 120MHz, assuming the voltage is higher than 2.7V I configured it with three wait states but the microcontroller crashes under high CPU load.
I see (based on https://github.com/underverk/SmartWatch_Toolchain/blob/master/src/driver_power.c) that there's a power management unit which probably powers the microcontroller, although Sony's site doesn't even acknowledge its existence. What is the voltage used to power the microcontroller?
The micro controller is fed with 1.8V. When in dfu-mode, it is changed to 3.3V.