Thanks for letting us know about the grid stripes issue - I can confirm this is a bug and we'll look to get a fix in for the next release. In the meantime, a workaround is to set the major ticks to be shown but to also set the tick line length to 0. This way there will be no ticks visible and the stripes will still show. Sorry for the inconvenience!
With regards to two stripes showing when zoomed out fully, I think this will depend on the amount of space available for the chart and so will differ from device to device - the tick marks are automatically calculated and I haven't been able to recreate this with your app on any of the devices I've tried it on here. It is possible to manually specify the frequencies of tick marks but it will then be your responsibility to handle changing the frequency when the axes are zoomed.