Micropython firmware for esp32

[tutu10]

I have an esp32 pycom wipy3.0 wifi Bluetooth module with a pysense board.
I have installed the firmware esp32-20180920-v.1.9.4-560-g185716514.
I thought that micropython is micropython but I have experienced so many strange errors (some times my programs run perfectly, other times the very same programs crash with mysterious error messages). So now I have the suspicion that I use the wrong firmware. But what is then the correct firmware? And where can I find it?