Are there any reported issues with the current atom feed based integration between OpenMRS and Odoo especially on reliability?
Some implementors have reported issues (FAILED EVENTS) with their OpenMRS and Odoo / OpenERP integration, but usually those are configuration / settings errors. You may need to check the failed events and see why / what error they are throwing and that can help isolate the issue.
If there is a misconfiguration, like a missing Product / Unit / etc, then every time that item is present in the Order, it will result in a failed event.