Sending Custom Object data via webhook when multiple COs can fire concurrently for the same lead

Hi all,

I'm building an integration where Marketo sends a webhook payload (via Mulesoft) every time a lapse-related email goes out, and the payload needs several fields from a Custom Object called lapseDetails.

From this thread I know CO field tokens don't resolve in webhook payloads — only {{lead.X}} and the standard namespaces do. The two known workarounds are: (1) copy CO data to lead fields via Change Data Value, or (2) have the webhook receiver loop back via REST.

Where I'm stuck:

Option 1 has a race condition. Producers can have multiple lapseDetails CO records insert concurrently (one per policy lapsing). Each insert fires its own campaign run for the same lead, and the flow needs a 1-minute wait (for an OAuth token). Both concurrent runs write to the same lead fields, so by the time the webhook fires, only the last CO's values remain. Both webhooks ship the same payload — one CO gets archived twice, the other lost.

Question:

Is there a Marketo-side pattern for sending the specific triggering CO's fields out via webhook when multiple CO inserts can happen for the same lead in quick succession? Ideally I'd like to solve this within Marketo rather than push the work to the integration team.

Thanks in advance.