Exception on ESP8266
Inconsistent behavior at startup is typically indicative of a bad power supply. The most likely issues are either:


The part is drawing more current during startup than your power supply can reliably provide.
The voltage of your power supply is rising too slowly, or is otherwise unstable during startup.


Note that the 3.3V regulator built into many FTDI parts can only provide 50 mA. This is what most FTDI breakouts use for their 3.3V output -- 50 mA is nowhere near enough current for an ESP8266, so you will see malfunctions if you try using that. Use a separate power regulator, or ideally a separate power supply entirely!