Sidebar code keeps on being automatically erased

I was just adding a “subscribe to email” button to the sidebar and it didn’t work properly so I removed it. I then saved the sidebar and it completely removed all the content in the sidebar.php file. I always keep a backup of the site and ftp-ed it to our server, but it keeps on automatically erasing the content in the sidebar.php file. I have no idea what is happening. Please let me know if anyone knows what to do. The website is https://www.orangepeel.co.nz and this is the sidebar code:

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