We had that problem and cleaning the seal didn't help. That ball is hinged and turned out one side had popped off. Got it back on and fine since.
(We had a visitor use the facilities who managed to cause the problem - I didn't ask for details).
2015 Shamrock 231KSS, Oyster shell
2016 Chev Silverado LT Z71 Ext. Cab, 4x4, 5.3L V/8
Reese Straight Line WDH, 2000W Honda Gen.
2 Old Town kayaks & 2 Boston Terriers - Zoey/Gonzo
Lar & Ruth
55 nights camping in 2015, 45 in 2016