There are a few ongoing issues that are potentially related to kernel bugs in NetBSD (possibly related to #50496).
There was a new NetBSD stable release, 9.3, that fixes a large number of such bugs. Perhaps some of the hard-to-diagnose bugs that keep cropping up have been actually fixed upstream. (I certainly hope so!)
I can send a CL to bump the versions in /x/build. However, as I remember, at some point, a member of @golang/release needs to actually create the image, or I can do that on a corp workstation and provide a link to an image.