Some staff slip tokens are missing from POST /circulation/check-in-by-barcode response

{
  "item" : {
    "id" : "459afaba-5b39-468d-9072-eb1685e0ddf4",
    "holdingsRecordId" : "65032151-39a5-4cef-8810-5350eb316300",
    "instanceId" : "f31a36de-fcf8-44f9-87ef-a55d06ad21ae",
    "title" : "The Girl on the Train",
    "barcode" : "765475420716",
    "contributors" : [ {
      "name" : "Creator A"
    }, {
      "name" : "Creator B"
    } ],
    "callNumber" : "MCN FICTION",
    "status" : {
      "name" : "Available"
    },
    "location" : {
      "name" : "Annex"
    },
    "materialType" : {
      "name" : "dvd"
    }
  },
  "staffSlipContext" : {
    "item" : {
      "title" : "The Girl on the Train",
      "barcode" : "765475420716",
      "status" : "Available",
      "primaryContributor" : null,
      "allContributors" : "Creator A; Creator B",
      "callNumber" : "MCN FICTION",
      "callNumberPrefix" : null,
      "callNumberSuffix" : null,
      "enumeration" : null,
      "volume" : null,
      "chronology" : null,
      "yearCaption" : "",
      "materialType" : "dvd",
      "loanType" : "Can circulate",
      "copy" : "",
      "numberOfPieces" : null,
      "descriptionOfPieces" : null,
      "effectiveLocationSpecific" : "Annex",
      "effectiveLocationLibrary" : "Datalogisk Institut",
      "effectiveLocationCampus" : "City Campus",
      "effectiveLocationInstitution" : "Københavns Universitet",
      "lastCheckedInDateTime" : "2019-11-01T16:51:23.315Z"
    }
  }
}