This is not an excuse, but.... This is a reserve engine, and that means it is a "crack slipping through" master. No one has it long enough or cares enough about it to do a full check or report what they find. Example: Their normal truck goes down for service after they check it, they get this "beater". Even in proper repair it's not up to modern standards. The next day's crew isn't used to checking it, and gets a job during the check. People get out of their way on the way to that call. Siren, two flashers and some driving posture is enough to move people and make you think the blinkies are in normal repair (says every medic/firefighter who has run siren and secondary lights). It's not an excuse, but it's a reserve and is rotated from home to home like the proverbial step kid. The abuse never gets reported...you get the point.
That said, polish that aero only in front of the par 36 flashers and I'll take it over a split fail blob of LEDs.
This truck just needs a pair of 900/m9 LEDs over the round holes left from removing the "grill lights". Gut the aero except the pars, throw one independent aero rotator in each side. Done.