This is due to the existence of the rfe_dat artifact in Clio's OpenURL. Removing it will resolve this. To do so:
- Look at the link created by the resolver to confirm that there is an element called rfe_dat.
- Remove the rfe_dat element from fields that your instance of CLIO pulls into the form.
- Add the rft_id field to CLIO to pull into the form, that field is the other place the OCLC number is located.