Compliance bot not getting some important messages

Hi
I am using a compliance bot to track calls that users are in. The webhook receives messages when calls are created/deleted and participants updated. Most of the time it works okay.

Unfortunately there is a problem- sometimes the bot will get a call created notification, but never get a corresponding call deleted notification. The easiest way to replicate this is as follows:

Compliant User A calls Compliant User B
Compliant User B picks up, but hangs up immediately
User A gets an error message on screen saying "Oh dear! Your call has dropped"
User B gets an error message on screen saying "Sorry, we couldn't connect you"

The messages received by the compliance bot's webhook are like so:
Created 721f0200-c51f-48c4-bd18-70e7af829f56
Created a31f0200-0420-4e4b-93c5-d605b4e8d8fc
Created 861f0200-ed1f-4785-851a-b4d0698854c9
Deleted a31f0200-0420-4e4b-93c5-d605b4e8d8fc
Deleted 721f0200-c51f-48c4-bd18-70e7af829f56
Deleted 861f0200-ed1f-4785-851a-b4d0698854c9
Created 481f0200-c91f-4b28-8dac-6749b3275886

That final "Created" never gets a corresponding "Deleted" so the user in question appears permanently stuck in a call. If I try to use the graph to access the participants resource for that call on communications/calls/481f0200-c91f-4b28-8dac-6749b3275886/participants I get a 404, so the call has obviously been deleted. If it was deleted why weren't we notified?

We need to be able to trust the messages arriving at the webhook are accurate in order for our tracking to be accurate. Please can someone shed some light on this?

Start by reproducing the immediate hang-up sequence and compare the webhook's Created and Deleted notifications with the participants resource for the reported call ID. Determine whether the missing Deleted notification is an event-delivery problem or expected lifecycle behavior; done means the behavior is corrected or clearly documented so compliance tracking can remain accurate.