Ontology builder job error

I installed the semantic search product from the marketplace. I complemented the pipeline with additional pdf datasets. The pipeline builder job completes and the dataset looks reasonable. This dataset backs an ontology object, and the update on that fails in OMA. The exact job error is:

Found [2596] invalid values in columns [mediaReference] of type [MediaReference]. Please check your datasource for the following:
  - Nulls inside arrays or nested arrays
  - NaNs or infinite values for floats/doubles
  - Misconfigured media reference data sources: confirm the data sources backing your media reference properties are correct and exhaustive
  - Malformed Geohashes: geohashes should be non-empty strings that are either
      (a) in the format `latitude, longitude` (in that same order)
      (b) a valid geohash encoding of a coordinate
  - Malformed Geoshapes: geoshapes can be invalid for a number of reasons, including
      - Non-conformance with the GeoJSON spec
      - Polygon self-intersection
      - Polygon consecutive coordinate duplication
      - Polygon contains unclosed rings (first point and last point must match)
    Consider running geoshape strings through the "normalize geometry" expression in Pipeline Builder to fix or drop invalid shapes prior to indexing.
Sample Primary Keys for invalid rows:
[[ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b_0_5], [ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b_0_13], [ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b_0_1], [ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b_1_4], [ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b_1_7]], failureMessages=[[]]

I checked the mediaReference column and the values contained in it are reasonable. Here’s an example:

{"mimeType":"application/pdf","reference":{"type":"mediaSetViewItem","mediaSetViewItem":{"mediaSetRid":"ri.mio.main.media-set.584c36ea-f9ba-427f-a3dd-43dfa4ff8955","mediaSetViewRid":"ri.mio.main.view.25b8a823-1537-4bec-8cb1-f54384586b63","mediaItemRid":"ri.mio.main.media-item.019506a9-2b33-7807-877a-06d49579e05b"}}}

How can I fix this error?