I don't really want to speculate, but given how the power issues have been so concentrated in time, I feel as if it must have a single causal factor, probably a defective pantograph? If it was just poor splicing, you'd expect those failures to be more normally distributed. I know they said in the board meeting that they inspected the pantographs on the proceeding cars, but precious little can touch the catenary, survive, and moves through the central tunnel and the GL system, especially given how steadily they've worked from Red Bridge through Copley and now St. Paul street. The pictures I've seen from the Friday and Saturday failures appear to be on the "southbound" track, the Globe notes that failure #3 on Tuesday in Copley was on the "westbound" (ie, "southbound") track and and pics of today's also appear to be in that direction. Do any C branch trips start from the GLX VMF?