Here I got something:
Feeding in 1Vpp 120Mhz sine wave singnal.
Trigger at below -340mV
A strange second waveform will start to appear and flicker. (Won't happen above this triggering level)
![](https://lh3.google.com/u/0/d/1Nj-OH5brSqstdtwY912dek2glKt-NcIk=w3840-h1969-iv1)
Edit: The sine wave signal was generated by a siglent SDG2122X(converted from SDG2042X). The oscilloscope was 50ohm terminated with the terminator from rigol and the BNC cable was from the siglent SDG. The oscilloscope was DHO804 on F/W 01.02 and was hacked to DHO924.
I have also tried lowering the frequency and it did improve as the frequency gets lower. However, it can still occasionally happen at 70MHz.
Edit 2: One more thing I want to mention is that the displayed Vpp on F/W 01.02 was noticeably higher than F/W 01.14, both hacked to 250M.
Edit 3: A source said that reloading the version-related FPGA bit inside the F/W package can ease this issue. I have tested this by reloading the BOOT.bin provided in the F/W upgrade package and it did help, but did not eliminate the problem.