Found my own answer.
For anyone having a similar issue, this had to do with the powershell script, the ConvertTo-Json requires an additional argument to convert the object beyond 2 levels, so I replaced this:
$params.attributes.meetings = $params.attributes.meetings | ConvertTo-Json
$params = $params | ConvertTo-Json
with this:
$params = $params | ConvertTo-Json -Depth 10
problem solved!