Second touch not detected for pan/drag on mobile when device is under heavy load

[blundellj]

Steps to recreate

1. Open a scene on iPhone 7
2. Turn on cut plane
3. Notice how Voyager's frame rate drops and becomes less responsive
4. Touch and drag one finger, notice that mode rotates
5. While keeping first finger touching screen add second finger
6. Notice that sometimes, the second finger press is not recognized and dragging with both fingers still rotates the model and does not pan the model