Ha, I thought that was only affecting my machine somehow. I have no idea what is going on, it feels like golang bug or kernel bug. I spent a few hours debugging that and I ended up with a dump of the data that failed to parse as YAML. Instead of the expected content I saw various corrupted data that I could not explain. No idea what the problem was.
Can you tell me which CPU you used? Did you use any virtualization systems? Can you tell me which filesystem you used?
In my experiments the problem reliably went away (as in, subsequent attempts had a chance to succeed) if I removed the source checkout and tried again. When I kept data on disk I got no success. Maybe the page cache was broken somehow?
In general I saw this only on Arch so I’d say it is a kernel-related change as the same hardware was successfully running Fedora and openSUSE.