I just took a flight from Moscow to D.C. and REX updates caused no problems (I was looking for the issue since you asked).  Perhaps it is involving another add-on you have?  Or maybe there was something about the weather... I dunno, but REX doesn't necessarily not play with the Captain.  Sometimes I think everyone gets assigned one random problem lol -- with me it is the sound issues that can't be fixed, Bill is having an electrical problem others don't have, some people get rocking on approach.  Maybe this is yours.