I cant use the furnance i cant do nothing on the furnace

Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here

What actually happened was...:
Describe what happened here

Steps to Reproduce:
1. Open furnance
2. But some blocks on the top
3. Try to go to the button to put ohet things or try to get my blocks back and i cant