Welcome to the Community,

growing of a thin provisioned virtual disk is usually caused by some guest OS (guest file system) actions. However, I can't unfortunately tell you what exactly is going on.

Some question though if you don't mind:

• does this occur at some specific day of the week, and/or at certain time?
• which Windows version, and build do you use?
• which file system is in use (NTFS/ReFS)?

André