That cheapo (or free) Cen-Tech is the worst offender. I found strings of solder and bits of wire in places where a slight shift while measuring house voltage could cause the meter to turn into a small flash grenade in your hand.
Even using it only on low voltage, low power circuits, I won't trust one. Some of the Cen-Tech's I recently bought had problems right out of the package. Our maker space had about 8 donated when we started it, and all have failed partly or completely.
Cheap tools cost more money.