FullStory namespace conflict. Please set window["_fs_namespace"].
Fortunately, there's a simple solution. Within the data capture script snippet, you'll see the following line:
window['_fs_namespace'] = 'FS';
Change 'FS' to an unused value, such as 'FullStory', in your code and it will resolve the naming conflict.
FS.identify() would need to be changed to