I usually backup my world every day by making a copy of it. It is larger than 1 GB, but it used to work fine until today, on 1.11.0. As you can see in the picture below, I get an error message.

I have seen that a couple other bugs such as this one have been reported, but they were all specifically for 1 GB + worlds in versions other than 1.11.0. My world has been over 1 GB for a while now, and it has always worked until 1.11.0.