The ESB brought out a commemorative booklet a few years ago, there was a piece in it when one of the first Drumm sets was demonstrated to Dev and govt big-wigs, the meet and greet was cut short, hence the batteries didn't get enough time to recharge fully. The technicians weren't 100% sure whether the unit would make it back to Dublin or stall before reaching its destination. In the event it got back (just about) rolling in under gravity alone for the last few yards.
Interesting mentioning sabotage and conspiracy theories, the big GSWR compound Sir William Goulding was alledged to have been tampered with, performance-wise, to make the so-so new 400 class look better.