SPWebs.Add returns site already exists every time

Hello,

I have a workflow that calls a sandboxed solution to create a subsite when ever a new item is added to a list.

false);

It frequently (nearly always) returns an error the site name is already in use:

"Microsoft.SharePoint.SPException:
The Web site address "/sites/Projects/KLTMZZX" is already
in use."

It throws this error even if I type unique gibberish in as site name.  Oddly enough, if I run it over and over, it typically will create the site on the 5th, 6th, or 7th attempt.  Does anyone have any advice on getting this to work in a SharePoint 2013 Online environment?