I know this is an old thread, but I was having this issue transferring from a VM (on a different unraid server) to the array. After trying a lot of things, I found changing to Q35 from i1440fx fixed it for me.
Edit: a lot better, but not 100% fix
I had my Swag docker still failing with the Letsencrypt cert renewal. My issue renewing was caused with Cloudflare proxing the traffic. I turned off Proxying for my A and CNAME records (under the DNS tab in Cloudflare). I then restarted docker and it came right. I could then go back to Cloudflare and turned the Proxying back on. Hope this may help someone else