The 202609190254 image built successfully, but long-story-short, it didn’t get fully uploaded to the servers. I think downloading the ISO would work for new installs, but - like you found - the updater isn’t seeing it properly.
We’re looking at some alternative approaches that would make that last part of the pipeline more reliable.
That said, the 20260919 image didn’t contain any significant changes from the previous image, so you’re not losing a lot by sticking with that previous one.
20260920 will contain bigger changes (we got a fresh rebuild of KDE packages for the first time in a few days), but before publishing that we’re investigating a failure in the QA testing. Could be a false positive, but we don’t know that for sure yet.
Things are certainly still a bit bumpy day to day as you can see, but in general we hold off from just mechanically pushing new images if we have test issues that we need to look at.