qui una soluzione di un utente dalla pag fbook del Mad per il problema dell'internal storage esiguo per chi installa da flashtool:
"ok i realised how to fix this (what i did wrong) i had to use smart phone flash tool to flash the Jiayu S3 5.1 RC5 rom as advised above however i had to use update firmaware to get it to load the rom. i then succesfully flashed the new 7.1 rom however i had the low internal storage problem. to fix this i wiped everything using twrp then went through the smart phone flash tool to flash the Jiayu S3 5.1 RC5 rom again but this time just using download option. i rebooted the phone and checked the internal storage it was back to normal. so then i went back into twrp and flashed the new 7.1 rom. all is now good with internal storage 3.3gb of 14.56gb used. hope that helps if anyone else made same mistake as me."