It's because you are running low on memory (RAM) of the device. The newer models don't seem to have this problem. The memory usage increases with the amount, size (and quality) of the images and the number of elements on the page (captions, special effects, overlay, borders etc). In other words, use the most minimal design and small to moderately sized thumbnails for mobile devices.
To achieve better mobile performance, try some of the following that you are most comfortable with:
- Decrease the amount of images on the page. Split up large galleries to smaller galleries.
- Use the Load More feature (can be set to only activate on mobile devices).
- Decrease the size of images for mobile devices: use the Mobile row height and Mobile row height deviation settings. The size of loaded thumbnails is equal to these two settings combined and up to 3x times that on retina devices.
- Use the JIG settings > General tab > Behavior of the plugin > Disable mobile hover interaction setting to get rid of captions, overlay and other effects that would otherwise react to mouse over and unnecessarily use memory and resources. Since there is no mouse (and subsequently, hover) on mobile devices it's feasible to skip the procedure of tapping the images once just to see the hover effect, and then open them with a second tap.
- Disable Special effects on mobile devices.
- In JIG settings > TimThumb & CDN, use 1.5 or 2 as Maximum retina density, also make sure that the Minimum retina quality is not a high number, as in larger than 50 (it doesn't need to be, see Retina ready demo).
- As a last resort, disable the Retina Ready feature.
- Do not disable TimThumb, else your thumbnails will be full-size images and consume too much memory.