Depending on how you overclock the specific RAM module, it could be that an auto OC setting (XMP), if that's what you use, apart from the RAM frequency also increses the DRAM voltage, and that is what is needed for the RAM module to operate normally. Timings can also be set automatically this way, resulting in stable performance.
If you specifically only bump the RAM frequency, and do not change voltage or timings, I'm not too sure I can explain why that works
But it is just a guess, since you have provided no information about the RAM or your system configuration or hardware