Today faces some weard problem with RB800. Why P-Troughtput is so low? Its major problem, coz true that RB800 i have connected lot of clients. 
Seems like lot of interference. Very low CCQ just 18/28.
Check if LOS is clear. May be some tree or building in between.
CCQ was 100% day before and now again its 100%. Maybe u’re right about interference. As far i checked - noone was on same band. Its 5Ghz bandwidth.