We will try to replicate it. We had a similar issue not too long ago, but I could not find the reference in the bug tracker. Perhaps it's in our service desk ticket system, it's currently in maintenance. But in the upcoming version, there is a sequence parameter in the Wizard that is used to avoid generating duplicate names. Perhaps both issues are not related, but they sound similar. I let you know asap.
The issue is reproduced. It is fixed in the new release by adding a sequence number. It adds up on each additional append. The new version is in alpha release. The beta is planned in two weeks.