I haven't had this issue. But I have read some reports here of others having it.
First a possibility... Have you had new tires installed recently? Many tire shops do not know how to properly jack up a trailer, and can bend the axles doing it wrong.
Second... If that isn't the answer.. It is really unlikely that a defect of this nature would show up after 5-6 years of use... So there is probably another cause.
I personally (along with some others) believe that most all TTs are under axled from the factory. They do not count any of the weight that is carried by the tongue. The axles are just barely sized to carry the remaining weight... This can work so long as perfect road conditions are the norm. But all it takes is the right circumstances in road conditions to momentarily overload the axles. Of course this would be a lot more likely to happen to a guy like me that boondocks and offroads routinely.. But it can still happen to a person like yourself that isn't as hard on their TT.
This of course is just my opinon... But I would probably replace both axles with higher rated ones.
Axles are really pretty cheap, and not that hard to install.
Or you could just replace what you have and take your chances that it won't happen again.
Myself, whenever something breaks, I upgrade it. I absolutly hate fixing something more than once.
YMMV