Even it is working on GPS port, it is not recommended to power it through Mindracer. as I mentioned before, MindRacer has limited load capacity and can only support small draw-out current. So use separate power source as possible.
The difference you observed between Telem1 & GPS port, I can not give a precise diagnose without examining the hardware. The description you gave about Mindracer not booting suggests there is something is drawing lot of current from MindRacer, which made the regulator can not output enough level of voltage supply to CPU core. I do not know what that is but it happens when you connect TFmini to Telem1. So a guess would be there is something about Telem1, either wrong wiring order, or a circuit short, or port been physically damaged somehow. You can use a multimeter to check if something similar happened.