Reverse thrust causes hesitation

Don't know if anyone else is experiencing this but on the 800NGX, when I press F2 to engage reverse thrust I get a freeze of about 1 to 1.5 sec. This has occurred since SP1.I remember having something similar with PMDG's original 737NG and I cured that by putting another sound set on, as opinion was that the hesitation or freeze was being caused by the reverser sound file starting. That certainly seemed to be true then.Could it be the sound file now? I don't want to change this sound set as Armen has done such a brilliant job.Iain Smith