I was exploring the end in search of end cities, and when I returned to the central island I attempted to jump through the end portal to return to the overworld. When I returned to the overworld I found I could no longer open my chests, use my bed, and when I mined a block it disappeared but dropped nothing. 

When I attempted to go back into the end portal to return to the end, I fell through the portal and landed on the obsidian underneath (I had previously converted the lava below the portal to obsidian). Despite the end animation in the portal, it reacted as though it was still an incomplete portal in that I feel right through.