The primay volume, volser, cannot be associated with swap device number, swapdev, because the scid of the primary is not available for the swapdev.
Determine which SCID is required using XQUERY VOLUME(volser) SWAP, and then use this in the command F ANTAS000, LISTDVCS swapdev scid to determine if you can terminate that session. If not, you will need to delete the volume and re-add so that SDM will register an unused SCID from the primary to the swapdev.
Extended remote copy (XRC).