It looks _too bad.
In my case it is a Geiger counter. Signal after shaper. Negative 2-5 uSec pulses arriving every 0.2-3 Sec. (natural background radiation). Level - close to 5v TTL. Triggering on ~1/2 amp.
Problem - triggering occurs only on a single pulse from 20-30.
It looks as if in a series of samples in the FIFO is a large sector of the “dead time” and, statistically, many samples fall into it. Or, may be, another similar effect.
For periodic signals, such as internal generator signal, the effect ceases to be visible. Because of the visual similarity of the periods of signal synchronization failures are imperceptible.
Checked all available firmware. In this respect, they are almost identical.
Sorry for my terrible English ))