Hi, this question is probably aimed at Charger as he appears to be a mine of info. I have recently started doing repair work for a supplier here in Northern Ireland (yes hot tubs have made it as far as here !). He basically supplies two lines of tubs, one American and the other Australian. We have had a lot of faults on pumps on the Australian tubs.( The faults are only showing now but the tubs have been installed for 3 years plus) These pumps are made by an Italian company called EMG. There is a plastic box on top of the pump body which houses two start/run capacitors.The values of these are 16 uF and 36uF (These are two speed pumps) In all cases the 16uF capacitor is totally fried, case melted, and its waxy contents emptied over the wiring inside this box. Any ideas about this. I would hazard a guess that the capacitor quality is not what it should be but I think there may be a manufacturing issue here.(See Photo attachment)

I would agree that it looks like a manufacturing issue, perhaps weak or low quality capacitors is the culprit. Caps fry when the dielectric isolating the two metal plates fail. That looks to be the case in the picture, and caused arcing in the can.

looks like an Aussie Maax spa with a Waterway pump/EMG motor.
we are finding this issue a common occurance on all Aquaflo and Waterway 50Hz 240v pumps, both single and 2 speed here in Australia over a few years now(although more recently improved).
the explanation is lower quality capacitors, but personally, i suspect the ratings may be a little low for the starting torque of some of these pumps. eg a 3hp (approx aquivalent to USA 6hp) impeller commonly shears off the shaft on one particular pump due to its extremely high torque (draws 45A on start up and runs at 11A).
Generally replacing the original cap results in no further call backs, and the failure rates have dropped off significantly, but ratings remain the same - perhaps better quality now.
Capacitor failures result from - incorrect sizing for pump/motor, low supply voltage under load at start up, low quality, age.
the image shown is actually rare - complete burn out - usually the cap simply fails with a visible bulge or small dielectric leak.