JiraPS - Set-JiraIssue, unexpected results

[Rene Nielsen]

Context:

Using JiraPS module, latest, and PowerShell 5.1. On Windows platform.

I am implementing automated creation and updating of Jira Versions as well as Jira Issues. This is regarding updating a previously created Jira Issue using Set-JiraIssue.

Objective:

Update the DueDate field in an existing Jira Issue using Set-JiraIssue. Below is what I'm calling:

$parameters = @{
  Fields = @{
  DueDate = $NewDueDate
  }
}

Set-JiraIssue $parameters -Issue $JiraKey

*$NewDueDate is formatted as a string with -Format "MMMM d, yyyy"

Negative Outcome:

Even though I am only attempting to set the DueDate I am getting the Jira's Summary field value changed (as reflected through the Jira web UI) to the text "System.Collections.Hashtable". And the DueDate field is not updated.

Request:

Please advise where I am going wrong.

I am using calls to Set-JiraIssue elsewhere (but without the parameters & Fields API syntax). I am successfully using the parameters & Fields API syntax in conjunction with calls to New-JiraIssue. I am currently stumped as to where I am going astray here and searching for clues that might resolve my problem.

TIA