Check your icons and if their name changed. If it has, you'll want to update the name in your instance. The following table gives you an example of how it would work.
Currently there is no easy upgrade option for SVG sprites. Each usage where an icon name is changed will need to be updated.
Upgrading Bare SVGs
In order to use Version 6 bare SVGs you'll need to copy the SVG code from the Version 6 download files and replace your Version 5 code with the new code.