Webhook responds "410" to Frame.io, "200" to postman

Webhook responds "410" to Frame.io, "200" to postman

Hi,

I am trying to configure a webhook trigger in Zoho Flow to be called by the Frame.io whenever there is an update in that app. 

After configuring the webhook and activating the flow, Frame.io always gets a "410" response which suggests that the webhook is not available anymore (unfortunately it doesn't show me the whole response, only status code and body). 

When I recreate the request in postman I always get a "200" response. After some experimenting I found out that the webhook (and subsequently the flow) is only triggered when 
a) I remove the "Connection" header
b) Set the value to "keep-alive"
If I set the value for "Connection" to "close" I still get a "200 OK" response, but the webhook (and flow) is not triggered. 

Frame.io seems to send its requests with "Connection" = "close". So this seems to be one issue with Frame.io. However, it does not explain why it always gets a "410" response  as postman always gets "200" responses. 

Is there a way I can make this work?
Unfortunately there is no App trigger for Frame.io yet. And I really want to avoid using scheduling or email notifications as triggers.

Thanks!