Good luck. After several years with the Warthog and breaking 2 of them myself, it became immediately apparent that the sphere you describe is nowhere near the quality of the rest of the stick/throttle. The sphere is cheap plastic and it is not smooth.....I fear that even when you get it returned the stiction will still be present regardless of the grease you use on it. I tried everything myself and a generous amount of white lithium grease was what I found best but it definitely didn't eradicate it.
If you are reluctant to go for the Mongoose base (which has no stiction at all) and has different cams to offer different centre detents I'd definitely recommend getting an extension. A 6-10cm extension gives more fine control and the additional length provides more leverage on the stick which means the stiction is drastically reduced. 'Milan' who makes these extensions is also a member on these boards and if you to the SimHQ buy and sell page
, his website link is on there and he's currently offering discounts (£28-32 depending on size). He ships from Croatia but delivery is quick to the UK and everyone who has one of these will undoubtedly highly recommend it.
There is also a thread about the Warthog and extensions here
....they're from a different seller but essentially the same thing. 'Sahaj' also has a website where you can buy the extensions from [link
] and he is based in Poland. I've bought an extension from both of these guys and they are both great quality.