Well, i guess there's no need to say that some active components (transistors, ICs (especially popular ones)) are very likely to be faulty/fake (real cap for current/voltage will be lowered af). I sure do love to buy stuff from aliexpress, but for components i need to rely on i would rather chose trustworthy retailers. However, you can buy passive components (not electrolytic caps tho) without having a problem using them.
btw, currently i'm waiting for LT3757 to arrive here from aliexpress, will see how it performs