The job goes sideways when what looked like a simple roller replacement turns out to be a track that's bent from years of a rough-running roller grinding against it, or a bottom bracket that's pulled loose from the door panel. On the newer doors typical to Medina, this is less common than on older stock - less rust, less decades-long neglect - but it still happens, especially on the roller closest to the spring side, which carries more load.
We'll always tell you straight if we open the track and find more than a roller problem. We don't pad a simple swap into a bigger invoice, and we don't pretend a bent track will be fine once new rollers go in - it won't. If the track's compromised, that's a track repair on top of the roller job, and we'll quote it separately before doing the work.