I had the same problem on my 17 - I would blow through at least one traveller car every season by moving it under load. I always kept a spare on the boat so I could switch out between races if I had to.

Since 1995, Hobie has been using an improved version of the traveller with larger diameter bearings. The catch is that it requires a deeper profile track. The deep profile track can be easily installed with just a drill and a pop-rivet tool.

Since I did the retrofit on my 17, I didn't have to replace the traveller car (about 2 yrs until I sold it) and it moved much better under load.

It's still not perfect, but it's class legal.