Hello Jocko, thank you for your input!
Partition reset thanks to fdisk and -u=cylinders command.
fvdw-sl 11 re-installed and upgraded to 15.3.
I face a problem when trying to upgrade to 16.1 now.
"/fvdw-sl-16.1-upgrade-04jul2021.zip" selected in firmware update menu, Control code : unzip then I get "Error: zip file inconsistent with your current firmware version"
Still get telenet refused when trying to use fvdw-sl console 6.0 18.1 (FW off and only one network card activated, ping is ok when drive is running).
I've been visiting the whole forum and I think I'm using the right process/files, I probably missed something again :dontknow
Bonsoir.