Powershell script cannot delete a directory
You are blocking yourself by cd $INSTALL_DIR\server
As proof of concept you can try following
New-Item $env:temp\server -ItemType Directory# by navigating to the folder we wish to delete we get an 'in use' error messagecd $env:temp\serverRemove-Item "$($env:temp)\server" -force -recurseExplicitly navigating out of the folder allows deleting
New-Item $env:temp\server -ItemType Directorycd $env:tempRemove-Item "$($env:temp)\server" -force -recurse