Without TAC support you can only work with the public download files. This is a procedure you could try but also may not work.
Save off a copy of your configuration before starting as a backup
Create a bootable usb on switch using snapshot
Copy the junos install file to the usb
Boot to the usb device
From the usb boot do an install of Junos on the internal media for the full format disk option. This should wipe out the corrupted files and start fresh for everything
Boot back to the internal drive