[Potential Bug] APIM Standard V2 SKU (preview) GatewayFailure at request-forwarder -> Value cannot be null. (Parameter 'promise')

Hi There,

We currently have a working APIM instance on a premium tier with internal mode in a VNET. Now we saw there is a new standard v2 tier available and also support vent so decided to give it a try.

So:

1. we created a standard v2 APIM in the west US region.
2. we connected the APIM with a Vnet on external mode. We have some internal API endpoints inside this vnet.
3. we created a simple api endpoint in APIM to call our internal endpoint. it was just a [GET] ping
4. ,however, we got the following error from App insight. looks like some internal issue with APIM itself.
   GatewayFailure at request-forwarder -> Value cannot be null. (Parameter 'promise')
5. At the meantime, when we try to enable the developer portal in the "portal settings" blade, we got "apim is not active error" but the status from the overview blade said "online"