Mine had similar issue.
Cliff explained to me what it is. I believe he is looking for a solution. I believe ECU will need a reflash.
See below.

"The engine signal has some variation in both amplitude and frequency
within one engine cycle as the speed varies due compression and power
stroke. Not to mention the glitches due to electrical noise The crank
smooths this out with its rotational energy but the effect is less at
lower RPM and opening the throttle makes it worse as more air to
compress and more power stroke. I think it is just exceeding the
expectations of the the ECU in filtering out false pulses. It seems to
be confusing the longer sync pulse as a missing pulse at the moment.
Fortunately it seems isolated to this off idle blip."

It should be noted that the two scenarios are using completely different sections of the map.
The slow throttle would be a fairly flat curve on the map going from bottom left and going up to the right and probably not getting past the bottom third of the map as it doesn't take much throttle to achieve 8000rpm with no load.
The fast throttle would be going steeply up the map and then right and probably then sloping downwards as the throttle is reduced.
An extra complication is the stable firmware has a throttle pump emulation feature (not configurable) so fast opening may be adding even more fuel that slow throttle doesn't.

This will help you view the map - https://mapvuer.myecu.biz/