Can confirm on the shorted/bad starter contacts. Back when I was just starting to learn TAC20's, this exact thing gave me fits. Using I/O injection I was able to force the starter to stay powered up while testing, and I could make it run, so I thought it was good. I felt pretty dumb afterwards, when it ended up being a bad contact on the internal relay in the starter. Lol. Since then I've ran into the same issue 3-4 times. I'm a fan of the Siemens starters overall, this is just something to watch for.