Originally Posted by repechage

failure has started. It won't heal itself. let's say you can get ahead of it with a stop crack drill on both sides, the stays are still less supported than they could be.
For a time is no object repair, I would detach both stays at the same time. fit in a reinforcement half sleeve, the stays will need to be re-mitered, and there is where the big energy will be spent most probably, always possible detaching the stays will also present hidden stress that will show up in the form of a bend or twist in the stays. The stays might be pliable to get in and dress with a spindle sander sleeve, unknown. then it all has to be brazed up again, keeping the alignment in check. Note too the dropouts were heavily filed back, that could be the next domino of failure.

The balance of the frame up front is not impressive, but it could just be the lousy paint, one headlug shows a curious crack in the paint around the outer edge of the lug shoreline.
if a repair was contemplated, get all the paint off by chemical means and assess for overheating of the tubes and cracks that are lurking elsewhere. Then take it to the builder.