However if the third chip on your memory stick is properly broken, then the third bit out of every word of memory may get stuck high or low, and then the whole chip is absolutely worthless.
The most expensive memory failure I had was of this sort, and frustratingly came from accidentally unplugging the wrong computer.
After this I did buy some used memory from a recycling center that had the sorts of problems you described and was able to employ them by masking off the bad regions.
Errors may be caused by bad seating/contact in the slots or failing memory controllers (generally on the CPU nowadays) but if you have bad sticks they're generally done for.
I've used it for many years. It only fixes physical hardware faults, not timing errors. For example if a RAM cell is damaged by radiation, not if you're overclocking your RAM.
