With some moves, there is only a certain time period in which a cancel is valid.
Your usual move has about ten-ish frames to cancel after its startup.
However, some moves can be cancelled before startup finishes, or the reception may start a while after startup.
Also, there are some cases where it will be recepted until a stun/recovery is finished, or conversely, there are moves where the reception time is extremely short.
If this timeframe is short, it will often be a cause of failure to cancel, and furthermore, if the startup is fast, it can cause misfires.