Yesterday have tried OTA I had huge issues…

Yesterday have tried OTA.
I had huge issues to make it work.
my setup
\- Esp8266
\- latest arduino IDE
\- lastest librairies for esp8266
\- Mac Os X
I manage to set it up with a simple code (even if i have to restart arduinio IDE everytime for the OTA to appear)
but when loading something a bit larger (<40% of the flash size). I come ito troubles it seems that the OTA upload process does not like the fact that I have SPIFFS on with some data in it. Indeed when reuplaoding the same sketch via USB => the SPIFFs does not work anymore. I reuplod the SPIFFS files and it works
Any idea ?