I have seen the photo taken for the burnt PNP transistor and I have read the datasheet for this transistor.
1. By visual inspection of the photo, the emitter is seriously burnt. The collector and base are fine. Although dark brown stain appears on the collector's pin, it is the burnt plastic coated on the collector pin as it is next to the emitter (pin and the plastic case package).
2. Based on the datasheet given and from your description on how the PNP transistor is used in your product, the transistor is not operating well below the maximum ratings.
Refer to the datasheet, -15A is the maximum (-ve sign indicates that the collector is the input of PNP), but -8A is the typical rating when the PNP is saturated (Vce) at room temperature of 25°C.
Refer to page 3 of the datasheet, look at plot "Forward Bias Safe Operating Area"
Ic is limited to a maximum of 11A when the Vce is 2V at room temperature.
14A will definitely "fry" this transistor even at room temperature, needless to even mention about operating it at higher temperture and higher switching frequency.
Notice that the switching frequency also causes increase in power intake. What is frequency used?
Reminder: This PNP used here has being designed such that the collector is able to take up higher current because it is the input, usually with a current-limiting resistor before it to protect the collector from high-voltage and high-current supply. Usually since the base is protected by limiting resistors and the hfe or gain of the PNP to ensure very low output current from the base, it is safe. But if the load side, where the emitter is connected, does not offer sufficient current-limiting protection, the emitter will "fry" under such circumstance.
If the PNP transistor is suddenly switched off, which results the input voltage at the PNP collector at the PNP input is lower than the emitter and load, the back current injection from the load will surge the PNP from the emitter. This back injection effect is made stronger from the inductor due to back e.m.f. (Lenz's Law).
Don't forget that the capacitor between emitter and load can discharge to the load and to the emitter of the PNP since it is the common path or node at the load.
I suspect there is no protection diode in series between the emitter of the PNP and the inductor.
There is however one diode which is usually used in step-down or buck converter but this diode is connected in parallel to the inductor and capacitor (capacitor parallel to load). However this doesn't protect the PNP emitter.
You can have the following protection method:
Connect a parallel power diode (1N4003 for example) between the emitter and collector of the PNP such that the cathode of the diode is connected to the PNP collector, anode of the diode connected to the PNP emitter. This is to ensure a flywheel circuit to provide a discharge path from the charged capacitor at the load to discharge stored energy via the PNP in a recursive loop. This also provides a dicharge path for the back e.m.f. from the inductor due to Lenz's Law. This diverts the huge injection current via the diode.
This PNP transistor only reported to fail recently because it has be used for some time. It worked for some time, but during the period when this PNP is working, the emitter bond wire between the die and the package pin is slowly fusing due to back injection until one day this problem occurs.