So I think there is some inconsistent fault in my circuit. I will investigate this.
Don't think its a fault, as that is normal for inductive load, like transformer, motor, vacuum cleaner and etc.
I know it sounds funny, its matter of luck, whether you switched on at the moment the mains line was at peak AC voltage, or at near zero, that will make huge difference, its like tossing a coin, literally.
Watch my thread as pointed by not1xor1 above, soon I will update my little project there, with details measurements (voltage and current) with/without softstarter, and also what happened when I switched a inductance load at peak or zero voltage, hell, this is also matter of luck if my scope can single shot capture at the right exact moment as yours, thru switching on and off like crazy perhaps.

Suggesting to read this ->
Beware of Zero-Crossover Switching of TransformersYour scope shots below is very similar to Figure 4.A at above document.
