I had the same issue: consistent packet loss (normally 1% - 2%, but sometimes spiking to 35%+) on both of my Azure VMXs in 2 different regions. When I placed a high load on the VMX's to/from Azure, the AutoVPN would drop. I tried everything noted above to no avail. I finally called Meraki Support today and spoke to Sanket who did a great job working this issue with me. He found a recent internal support article related to this issue. The VMX setup guide failed to mention this configuration item and has since been updated as of October 2021. To fix the issue, login to your Azure portal and open your Route Table(s). Select Subnets and disassociate the subnet that both the Azure Router and VMX Router share. In my case, it was subnet 10.100.0.0/24. Azure default gateway was 10.100.0.1 and the VMX was 10.100.0.4. I'm assuming the two were fighting over the traffic and causing the packet loss. After disassociating the subnet, the packet loss stopped, performance noticeably improved, and the AutoVPN drops stopped. I didn't experience any routing or connectivity issues. No downtime was incurred either when I applied the disassociation in Azure. I hope this helps anyone who's been troubleshooting this for months like me.
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