m92 /flash/media in read only

hi...i just noticed a problem i have with my m92 since a couple of day.
it look like i'm unable to delete files from the internal storage.
if i connect with gserial and launch a dmesg it seems some errors are present on my related file system

AT: Filesystem error (dev mmcblk0p3)
fat_get_cluster: invalid cluster chain (i_pos 0)

this is /etc/fstab entry

dev/mmcblk0p3 /media/flash vfat loop,iocharset=utf8,atime,umask=0 0 0

and /etc/mtab say

/dev/mmcblk0p3 /media/flash vfat ro,relatime,fmask=0000,dmask=0000,allow_utime=0022 ,codepage=cp437,iocharset=utf8,shortname=mixed,err ors=remount-ro 0 0

another strange thing is that according to fdisk /dev/mmcblk0
partition 3 is toggled as linux

i guess i should do an fsck but the command is not present in busybox.
how can i fix the file system?

can i move away the files and format the internal storage? how?

many thanks