Just wanted to follow up - the issue for us turned out to be an app installed during the TS forcing a reboot outside of TS process (which is why our SMSTS log wasnt really helpful). Once we got that sorted out, works like a charm.
Has anyone had luck with adding decision logic to this? We only want the TS to proceed after the technician has clicked OK on the message. It looks like the TS is continuing for us after getting the exit code, so the message only displays for a few minutes. Thanks so much for what you've done for the SCCM community anyweb... these guides are great!