@nebulon Thank you for your response. I checked database integrity in LS and deleted old surveys. After this operation, update run smoothly in Cloudron ... thank you!
@nebulon Hi Johannes,
I have just updated to the latest version of LS and it seems to be OK.
Thank you very much for your help. I have learnt how to use backups 🙂 and my takeaway is that it would be better to update manually (and backup first).