Not always reproducible; it seems to happen randomly. This is an absolute show-stopper sometimes. Sometimes happens and sometimes doesn't under the exact same conditions. If this is in any way connected to 3rd party plugin use, please make Pro Tools more compatible with 3rd party plugins. Pro Tools seems to have problems with all the major plugins on the market...Waves, Slate Digital, Blue Cat, Oxford Sonnox, to name just a few. I actually get -9173 errors sometimes using only Avid stock plugins with an approved PC, all optimizations done.