I own an appartment in the residential, 2-storey building in Edmonton, AB, Canada. There is an older oven that always worked well with no issues. I recently cleaned it thoroughly. 

In the process, I unscrewed 2 crews that hold the top heating element and after cleaning, screwed them back in. Now, when I turn the oven back it works fine for about 10-12 minutes, but then the power in the whole appartment goes off. After about 15-20 minutes the power comes back on. No breakers are tripped. I have 2 questions:

1. Obviously, my removing the heating element caused some issues with the oven. What could they be? Should resetting the element help? Should I replace the heating element? Should I replace the stove?
2. Why would this issue cause the power in the whole appartment to go off. When the power goes off, no breakers are tripped and the power loss is confined to my appartment only.

Thank you for your help.