B747 Not Following Flight Plan from Simbrief

I have an OFP loaded into the ac from Simbrief and for an hour or so everything was working correctly. Then all of a sudden (maybe I touched something accidentaly) the EXEC light came on. I pressed it and the ac went into a right roll and stayed there. I copied and pasted a waypoint into the MCDU legs page and activated and executed. But it would not resume the FP. AP is engaged, LNAV and VNAV modes on. Turning them on and off does nothing. Going into heading mode does nothing. I’m using the DEV version, but this is so basic that unless they don’t do any testing whatsover before publishing this shouldn’t be happening. I will install the stable version, but I suspect there will be so many inop pieces that I won’t want to use it. Unless someone has an idea other than uninstall and reinstall - which I just did prior to this flight.