Measuring at 20uS, I can massage the trigger to detect the first voltage drop: https://ipfs.io/ipfs/bafybeiggijiystskmrgdocvczfoqqulvfnzuktle7cuwy73kqpjyo54tkq

It turns out the voltage scale is wrong in the pictures, because I tried to zoom out by setting it to 10. I think it only affects the next recording, unsure. The gradiations were set to 1V for the recording.

Farther to the right there are visual corruptions that go off the scale and report multi-ten p2p voltages: https://ipfs.io/ipfs/bafybeibyzmeqcqa24rkib6gleg74jmg44ztny4vev23qg6ua7jthk5b4ym

This seems to happen associated with viewing a signal farther into the buffer. I might guess some kind of memory corruption. It makes sense that memory corruption would appear this way.

My first idea was that the signal could be oscillating so fast that it misleads the analog-to-digital converter. I'm guessing this isn't the issue, because after measuring a couple times it seems more associated with buffer position.