In repetitive mode the waveform is constructed by triggering the acquiring data on successive repeating events. (If signal is repetitive, like a system clock, a very accurate waveform can be constructed from repeated acquisitions). Data is randomly captured into a circular buffer through a A/D converter.
THEN a fine interpolator is used to precisely (40 psec or better) measure the time between the last sample taken, and the analog trigger event. That data is placed in a memory buffer. With successive acquisitions, buffer gets filled. (Purpose being high bandwidth achieved using relatively inexpensive A/D converters).
Your interpolator is out of calibration.
