The team are currently investigating an issue as several customers have noted this. We can see normal volumes hitting our API, and going through the system, but there is a noticeable drop off in what's being ingested into the data store itself. Not sure yet what's going on here, but it is under active investigation.
The status page here is being kept up to date: https://status.raygun.com/
It appears to only relate Crash Reporting, not RUM or APM. As you note, the data is making it most of the way through the pipeline, so is triggering notifications. I'll update this thread when it's resolved.
Sorry for the inconvenience Greg!