I did back in ~2017 or so while I was working at $BIGAZURECUSTOMER. It was tough getting a hold of the right person in support, so we pulled some backchannel strings. Turns out an update to their hardware had disabled ECC on some switches.
So it seems this is their software defined network, the packets still look good when entering via the microsoft edge routers and they get bitflips on their way into our express route
I also have a follow up to this topic. I would say it looks like in Azure nobody is verifying TCP checksums. A bitflip in tcp payload should have been noticed at the NIC/tcp level but it reaches my application with corrupted data.