When i used to take quick photos by double pressing the power key, its usually takes time to save showing "in Processing" and during this if i minimized or go back then photo doesn't save any more which decrease the quality of Nokia Camera. Missing the special moment picture when need to take quickly. Even during normal photography takes time of 3-5 second to save the picture. Its too slow saving process, "In Processing" saving option should run in background so we can take more photos quickly. Please Fix it ASAP.
I fixed this issue by resting camera setting, pls try the same, hope this will helpful for you.