OK, I have the following observation concerning T32 programming:
I use win8.1 and a custom modified teensy_loader_cli, that allows me to download the same hex file to multiple Teensies on USB.
All teensies run blink (blink_31.hex) with USB-serial activated.
attept to re-download blink_31.hex
case1: single T31 on USB hub: no problem, Com disappears, hid comes up and programming starts
case2: single T32 on USB hub: COM disappears but hid does not come up (loader cycles around teensy-open()), needs pressing Program button
case3: T32 AND another teensy (T31,T32): one teensy after the other will be programmed fine.
adding delay before usb_init did not change this behavior.
I attach my cli-loader with blink_31 for others to reproduce.
I do not publish source code of loader, as it uses reboot code from Paul, of which he stated that he will not support, and I cannot support it.
(Also there are other cli loader around that are more professional than mine, which is specific tuned to my needs, and Windows-Only)
I acknowledge that my configuration is not typical, but I find this behavior, if verified, interesting and maybe useful for Paul.
Paul, if you wanted to investigate (after HaD) , send me a PM for modified loader code.