The forward-right rifle lowered crouch run (AmovPknlMrunSlowWrflDfr) is slower than the other rifle lowered crouch running directions. That is, when your rifle is lowered and you are crouched, pressing W+D is significantly slower than, say, W+A (i.e. the forward-left direction).
For a comparison, AmovPknlMrunSlowWrflDfr (forward-right rifle lowered crouch run) is 8 kph where as AmovPknlMrunSlowWrflDfl (forward-left rifle lowered crouch run) is 10 kph. It seems AmovPknlMrunSlowWrflDfr has a duration of 2.1 seconds which is a bit longer than all the other directions. Not sure if this is directly related, just something I noticed.
I can't find any reason why moving forward-right should be slower than moving forward-left in this stance, so I assume this is unintended.