I tried the conversion and ran into the same issue.  I do not have any bundles active or inactive, so that solution doesn't help.  I renamed the parent product to a unique name "2 Consulting", and the same error comes back.

You can't merge 2 Consulting because 2 Consulting already exists. To make this change, you'll need to give 2 Consulting a new, unique name or go to the Products and Services list to give the other 2 Consulting a different name