Powershell Runbook: Parse Webhook Trigger works in Test Pane, Doesn't work when triggered by Events

Question

Powershell 7.2
HybridWorker

The runbook is configured to be triggered by webhook as a "pre-event" for Azure Update Manager.
When I test in the "test pane" with an example webhook from a failed job in the logs, the script runs correctly.
When it is triggered during the update process, the Webhookdata gives :

NotificationPayload = ConvertFrom-Json -InputObject $WebhookData.RequestBody

Cannot bind argument to parameter 'InputObject' because it is null.

I tried using snippets directly from Microsoft Learn documents, they didn't work either!

Things i've tried:

• Online i've found people saying there were issues with PWSH 7.1 and parsing, and tested using regex switches to "properly" escape characters. Would work in Test Pane, not when called.
• tried converting the whole webhook out from json, then trying to pull the individual values, same outcome.
• tried adjusting the syntax a number of ways i don't have all recorded here.

This has been haunting me for over a week now, does anyone have any insight on how to get this to work?

OH! also, if there's any tips on how to fix the error/output stream to not generate all those "[" and split the logs into 24 inddividual log entries, that would be really appreciated too.

Thank you!

##most current test
param 
( 
    [Parameter(Mandatory=$false)] 
    [object] $WebhookData 
) 

write-debug "Script with New syntax: " 5>&1
$notificationPayload = ConvertFrom-Json -InputObject $WebhookData.RequestBody
write-debug "Notification Payload is : `r$notificationPayload `r `n" 5>&1
$maintenanceRunId = $notificationPayload[0].data.CorrelationId   
write-debug "MaintenanceRunId is : `r$maintenanceRunId `r `n" 5>&1
$resourceSubscriptionIds = $notificationPayload[0].data.ResourceSubscriptionIds   
write-debug "resourceSubscriptionIds is : `r$resourceSubscriptionIds `r `n" 5>&1
$eventType = $notificationPayload[0].eventType
write-debug "EventType is: `r$eventType `r`n" 5>&1

##Original version of my script, based on script from here: 
## 

param 
( 
    [Parameter(Mandatory=$false)] 
    [object] $WebhookData 
) 



Connect-AzAccount -Identity 
$notificationPayload = ConvertFrom-Json -InputObject $WebhookData.RequestBody 
$eventType = $notificationPayload[0].eventType 


$notificationPayload = ConvertFrom-Json -InputObject $WebhookData.RequestBody 
$eventType = $notificationPayload[0].eventType