Potential frame rot?

Looking at it more it looks like POR 15 was applied to that section of frame rail ahead of the outrigger brace. There’s some scale on the frame near the holes at the edge of the picture, and then some places where the POR15 is peeling (which it’s known to do).

I dunno, the rails behind the repair look ok, as do the other pictures. Thing is that “frame repair” and structural integrity are pretty blurry on these cars. It’s all just sheet metal, and pretty much all of it contributes to structural integrity. Patching a frame rail isn’t all that much more structurally important than repairing a floor pan. Heck repairing a small section of frame rail is easier than replacing a floor pan.

Just indicates you’re going to have to look at everything more carefully.