I have a world with a store based on the XP level, I have this world since the commands came to MCPE and it has always worked.
When I downloaded the beta I discovered that the command that takes the xp from the players doesn't work.
I tried with lowercase "l" and uppercase "L"
I always use "/xp -10(or any other amount)L @p" and well... it doesn't work.
I tried with giving xp and it doesn't work neither.
Thank you for your report!
We're actually already tracking this issue at MCPE-79470, so I will resolve and link this ticket as a duplicate.
That ticket has already been resolved as Fixed. The fix will arrive in the next version or is already included in an available version of the game, you can check the Fix Version/s field in that ticket to learn more.
If you haven't already, you might like to make use of the search feature to see if the issue has already been reported.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – ✍️ Feedback and Suggestions – 📖 Game Wiki