（1）Type of sample, degree of degradation of the sample: For example, an FFPE sample itself has a certain degree of degradation, and the degree of degradation varies, the range of fragments interrupted by samples with different degrees of degradation with the same interrupting conditions will also be unstable.

（2）The system was not mixed well: It is generally recommended to blow and mix well with a gun after the interruption system is configured. Failure to mix well may cause unstable interrupted lengths.

（3）Interruption temperature: The PCR temperature during the interruption will directly affect the interruption results. It is generally recommended that the PCR instrument should be calibrated regularly. During the experiment, if the PCR instrument drops to the interruption temperature, the PCR system should be placed in the PCR instrument.