Yes it is a triac. My guess is that the yellow capacitor is a dropper for powering the overload/soft start, and it has degraded from noise to the point where it no longer can power the overload circuit. Probably a 1uF part, and probably has degraded to around 200nF with the spikes it has to handle.
To check connect the upper blue to the upper black wire on the module, and the lower brown to the lower black wire, and turn it on. Careful, this will kick a lot on power on, as there is no longer soft start, but will prove if the controller module is failed. you probably can depot the capacitor if the potting compound is a soft type, but if it is a hard type then you need a new module.