The following session relevance query will return all Fixlet IDs (this will include Tasks, Baselines, Analyses, etc…) that have at least one duplicate, as well as the number of instances of that particular ID:
(it, multiplicity of it) of unique values whose (multiplicity of it > 1) of ids of bes fixlets
That said, as others have suggested, Fixlet IDs are only unique within a given Fixlet Site. It is absolutely expected that the same Fixlet ID can (and will) exist across Fixlet sites.
It seems like the SQL queries in question may need to be updated to account for this?