UPDATE:
Ok, so I worked a QSO with a local ham friend.
It started again, with a TX6 "CQ RU.."
The QSO went as a standard QSO, meaning NOT with AZ (the FT RU exchange), but with the std. grid square.
The QSO completed and promptly went back again in keeping the CQ RU.
I found that it won't clear by hitting erase, etc. The ONLY way to clear out the incorrect RU part, is to end WSJT-X, then restart.
73 John