There are two likely issues apart from the supply. First is the cable from the supply. Shorter and thicker is better. It doesn't matter how good the power supply is if the cable drops too much voltage, and you'll struggle to measure voltage spikes without decent test gear. Second, overclocking is never guaranteed Chips are manufactured to a specification covering a range of speed, power supply voltage, temperature etc. Where there are multiple chips (RAM, peripherals, etc) each has its own range of parameters within which it will work. Sometimes these will only overlap quite near the nominal operating conditions. Overclocking requires all parts to be able to work equally well outside of these intended specifications. Sometimes it is easy. Sometimes it's almost impossible. Sadly, the culture around devices like the Pi encourages users to try things like overclocking to the point where it is expected that it will always work. Sometimes it won't. And if it does, the speed increase may not result in a proportionate time saving if other elements (like USB / SD storage) still take just as long.
(And for the mods... Why does the forum software treat the word "s-c-i-e-n-c-e" as censored and not permissible in posts?)
