I have frame less windows and so far they have been trouble free although I do have one that has the slide mechanism issue. There is a wheel that is off track.
It appears to have been improperly installed that way from day 1. It is a simple fix but it appears window needs to come out to fix it.
I simply avoid the issue by not opening that window. Not a real solution I know but I seldom open my windows anyway.
Track issue aside the windows are great. I prefer them over the traditional windows. The track issue is not a failure but the result of a poor installation of that particular window.