cannot assign batch tags

When I select one or more samples from the sample browser and apply modifications to their tags, I get an error

Failed to add samples with HTTP 400 error:

{
  "message": "Got DIRAC error: ValueError('oldTags is out of date'): oldTags is out of date"
}

and the tags are not modified. If I click through to the individual sample and edit the sample tags, it works just fine.

Without being able to make batch tag edits, the analysis productions system becomes extremely unwieldy.