Default Internal Storage Corrupted?

Hello everyone,

A couple of days ago, my G900H started disconecting from the networking randomly, until it became unable to read my SIM Card. I tried with another SIM Card but got the same response, so I figured the SIM Card reader (or something from inside) was broken, so I send it to repair with no success. So no, I'm flashing stock roms from another country to see if something's changed and I notice that I have unknown baseband/No IMEI, so I go to EFS Pro to restore a backup I made of my EFS Folder just in case something like this happened, and when I restore it nothing's happening! So I tought that maybe the phone's internal storage is broken (damaged or corrupted). Is this possible? Has anyone experienced something like this?

Thanks in advance for the replies!