Red Bull posted their first double retirement since the 2010 Korean Grand Prix last weekend - and in this era of ultra reliability an engine issue has left the champions and their suppliers baffled.
Red Bull had a weekend to forget in Italy after Sebastian Vettel ground to a halt with alternator failure on lap 47 and Mark Webber pulled into the pits to retire two laps from the finish; his car un-driveable after he flat-spotted his tyres in a spin.
Neither was in contention for a podium - Vettel dropped out while running sixth and Webber had been in the lower points positions for most of the race - and while the loss of points is disappointing it is the alternator failure on Vettel's car that has caused most concern.
It's rare for such a part to cause any issues but Renault alternators failed twice in Valencia - on Vettel's Red Bull and Romain Grosjean's Lotus - and also caused Vettel to stop in practice at Monza before his issue in the race.
An alternator provides the electricity to power all the car's onboard systems - making it an absolutely crucial part of an F1 car.
The heavy demands on electronics for engine management, gears, sensors, fuel pumps and so on creates a constant demand for electrical power and the unit, which works as a generator, basically converts some of the mechanical movement created by the engine into a 12v feed of electricity as the car travels around the circuit.
As it must provide power at all levels of revs, the alternator is designed to generate enough power at low engine revs to run the systems and at higher revs it feeds extra energy into a small battery which works as a buffer - similar to the way the buffer works when streaming online - to store extra capacity in case anything temporarily happens to reduce the generation of the alternator.
Without the alternator working, the battery is not large enough to run for long before it leaves the car with no power - as could be seen last weekend when Red Bull were forced to make frantic radio calls to Vettel telling him to stop the car immediately when the juice ran out and all the systems shut down to avoid blowing one of the eight engines they have for the season.
Given its size and bulk - it weighs in at around 750g and is just 5cm in diameter and 7cm long - the alternator has to function in extremely tough conditions, with internals spinning at up to 19,000rpm and its location close to exhaust exits and the engine block, which can get very hot.
All manufacturers' units have heat shields and most have airflow around this to move the heat away. Some are even water-cooled, with water jackets to take away the heat. In hotter ambient temperatures, however, or in cars with more compact packaging, the heat cannot dissipate so well and it is prone to overheating.
Teams can monitor the alternator's health from the pits via telemetry, constantly checking power and temperature, which is how they knew when to tell Vettel to call it a day.
After Valencia, Renault instigated a short-term fix to reduce the electrical load on the car and improve electrical generation at low speeds - but that, of course, comes with compromises. After continued analysis, they introduced a design with greater capacity, which they thought would solve the problem.
But at Monza, Vettel stopped in FP3 and then also in the race and Lotus had also made a precautionary change on Jerome D'Ambrosio's car after an alternator issue in qualifying.
Now, however, these multiple failures could help Renault find the answer.
Taking the different stages of failure - from the part that was close to failure, the one that failed and the ones that were OK - they can effectively reverse engineer the part and evaluate the best solution.
Further modifications to the design may be needed, but testing them to confidence levels before the next race will be tough. More likely is the option of changing acceleration maps so running is less severe - but that will compromise engine performance - or asking teams to increase cooling around the unit - but that compromises aerodynamic performance.
Initial analysis points to a low-rev problem, suggesting the generating capacity at the baseline is not high enough on circuits with slow corners and that is exacerbated when the ambient temperatures are high.
All those factors are in play at the next race in Singapore - so Renault had better act fast if they are to find a solution.