Sorry for the spam but I found how to fix in order to update shelly device.
I did on Wave Shutter and I was able to update one unit.
file to modify
core/ajax/zwavejs.ajax.php
Row 231 in my version.
Session
if (init(‹ action ›) == ‹ uploadOTA ›) {
if (!in_array($extension, array('.bin','.hex','.ex_','.gbl'))) {
throw new Exception('Extension du fichier non valide (autorisé .bin, .hex, .ex_) : ' . $extension);
Add .gbl in the valid extentions