I'm getting a couple of small glitches with Rockbox.
The first is that it sometimes gets stuck for a few seconds when scrolling through file lists. I just have to wait and it always starts moving again eventually. The file lists aren't that long and probably no more than two screen's depth.
The second seems to be related as it gets stuck when I move from track to track while it's playing. The counter showing the elapsed time will stop and nothing happens for a few seconds and then the file will start playing with a loud "crack" as it does so. It happens about one time out of every three.