The East Coast Main Line is prone to dewirement (where the pantograph comes off the catenary and normally gets tangled and brings down the wire) at an unusually high rate. The folk wisdom is that the use of wired headspans instead of rigid portals, combined with a long distance between stanchions, makes it fragile. I don't know the extent to which that's true.

Set against that, the miles per technical incident for electric trains are about twice that for diesel, and a train breaking down on the ECML is also disruptive, if not obviously infrastructural...