I saw your post on another thread, you simply don't understand how polling rate works. The mouse is being polled at 1000Hz, if there is no information there because it's moving slowly it will log lower numbers.
You can't force a thing that doesn't exist. If you are moving slowly the updates in mouse position from sensor to mcu will be slower. That's how a mouse works, try to wrap your head around it.
That said mice do have slight inaccuracies based on speed even if the are considered low srav (no acceleration in layman's terms). If the position moved is on the line between the physical, or logical, pixels in the array the mouse cannot detect on which side it's on so there is a slight deadzone inserted to avoid jitter between one position and another.
Surface, cpi, and framerate all play a part in this and if by any chance you're using a pte (or a viper at high cpi), well lol.
"a bad joint can't be that bad right?" -q