I'm pretty sure it's not a problem with HOTAS Warthog, but a game bug.
I assigned the "hotas slew" axes to another joystick and got exactly the same symptoms.
The bug is easy to reproduce and consistent. Assign the "HOTAS slew" to analog axes, and try slewing in circles or "eights". Each time the stick crosses diagonal the sim loses track of one of the axes, causing intermittent motion, out of sync with the stick.