Actually I wanted to post this in the bugs forum but formally this isn’t a bug I guess. If you create a gantt chart you have the option to use html5 or html. The result of html5 however is a gantt chart in flash which is not supported by IOS. I think that’s an issue.
If you choose html then you get a jschart which does showup, but the gantt chart part has a different height then the tasks left causing a gap at the bottom. The task is not exactly besides the corresponding chart.
