The EML parser: https://knb.ecoinformatics.org/emlparser/parse
no longer traps datasets which are missing their customUnit definitions in metadata. I.e., this passes the parser (no additionalMetadata section)

:

<eml:eml ...
  <dataset>
   ....
              <unit>
                <customUnit>millimetersPerYear</customUnit>
              </unit>
  ...
  </dataset>
</eml:eml>

Test doc is uploaded (with extension .txt for github)
edi.9.0_2.1.1_custom_unit_missing.txt