Hello WOLF_OF_DK,
the re-installation at the loader prompt would be the right procedure. For me it seems that your installation image is corrupted. Please download a new image and perform a checksum check, if it matches with the provided checksum on the Juniper download site.
E.g. for JUNOS 18.2R3, the command you should use looks like:
install file:///junos-srxsme-18.2R3.4.tgz