The generators had input quill shafts that were a bit weak. After the gen is switched on, it takes a while to get up to its load-bearing speed, and if you bung on electrical load too soon, the quill shafts can shear. Expensive.
Nice-looking sim, by the way! Yours looks like a Widebody variant, which is probably a 109A Mk 2 plus, with the C variant Allisons.