If you use the fill command in Minecraft BE, you cannot use it in the available location with the phrase "You cannot install outside the world".

Thank you for your report!
We're tracking this issue in MCPE-154009, so this ticket is being resolved and linked as a duplicate.

If you would like to add a vote and any extra information to the main ticket it would be appreciated.

If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.

Quick Links:
📓 Bug Tracker Guidelines – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki