By the time my tread endcap screws started showing rust, it turned out the tube coupling nuts "wings" had rusted away so that the ladder standoffs were loose, so I replaced them in both the standoff and the attachment plates for the ladder
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You can get the tubing coupling nuts at
McMaster Carr, if you can't find them at the hardware store.
The standoffs on mine used 1/4"-20 Panhead machine screws, while the mount plates used 1/4"-20 Flathead machine screws.
Installing new coupling nuts, using a socket and tapping into the 1" ladder tubing with a hammer to the desired depth (shown below) was much easier than removing them :D
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