That's a bug, thanks for reporting

(didnt test with scout, d'oh!). Will look at it either today or tomorrow.
EDIT:
Okay, so the issue was with applying a custom airstrafe multiplier to the scout. I've decided the easiest and most intuitive way to fix this is to just allow scouts to be ignored for the airstrafe-modifying. So I've added a new cvar "fc_airstrafe_ignorescouts", which defaults to 1. If you download the new version (1.0.1) all should be good.
I've had brief thoughts about other fixes for this. Among the things I thought of were:
* Only apply airstrafe modifier when the distance-to-ground is higher than a certain value.
I decided against this because:
1. Compared to the issue I'm trying to solve, it takes too much effort to implement.
2. This would be non-intuitive for players, possibly resulting in frustrating situations.
* Set up a special double-jump routine myself.
I decided against this because:
1. It takes more time to implement then my current solution

.
If anyone **really** wishes to block airstrafing on scouts, tell me so, then I might implement this.