Hi Fabio,
Thanks for reaching out with your BoldGrid Post and Page Builder questions. We were unsuccessful in attempting to replicate this issue on Firefox.
The drafts in our dev environment are saving properly in the browser and not displaying as published as you mentioned. When did first notice this issue occurring? Was it perhaps after an update of Post and Page Builder or your WordPress core application?
Can you please verify for us that you’re using the most update versions so that we can troubleshoot further? It would also help it if you send a list of your active plugins so that we can test this issue with the setup that most resembles your own.
We look forward to assisting you further with this.