Improvements in placement of timing patterns in self-servowriting include detecting and correcting for media defects. A detector is used to detect whether a trigger pattern is within an expected location on the storage medium. If the trigger pattern is not detected, then a physical defect may be present. Thus, in one example, a false trigger pattern is generated. Additionally, a determination is made as to whether a trigger pattern is within an expected trigger pattern region. When the trigger pattern is not within the expected range, then a valid interval window may be modified to adjust the expected trigger pattern region.