Hi,
Thank you, but that did not help.
After testing extensively on a cloned version of the site it appeared that when deleting some lists from V5, I could then migrate everything in V9. I then came to realise that the lists that were fit to be migrated were those for which no languages were defined in V5, or set to 'all' in the database. I updated all lists straight in the V5 database and set the column 'languages' to 'all', and bingo, the migration process went through like a charm, including the subscriptions of the users... Pfffiouu.
Perhaps something should be updated accordingly in the migration script???
Best,
Antoine