OK, so I have:
1. Emptied out the overrides folder /language/overrides (to prevent possible syntax issues)
2. Re-test with VM registration. For example, missing is COM_VIRTUEMART_REGISTER_EMAIL.
I look in /languages/it-IT.com_virtuemart_shoppers.ini and it is there though!!
3. Download fresh Italian language pack and install:
https://virtuemart.net/community/translations/virtuemart/it-ITStays the same
"use english as fallback for untranslated strings" is selected
no fallback is UNselected
Custom fallback now set to en-GB but no difference.
Screenshot and log attached are from the en-GB VM registration. I do not see any native JM translations missing, only VM.
Any clues on how to debug this situation?