On several occasions I have had proximity false alarms occur while flying toward the sun. The first time it happened the P4 was heading into the sun, 500 m upwind from Home, at 100 m altitude. It made complete stop. I tried different stick inputs, but I could get was vertical motion. After switching to S mode, I was again in control and was able to get home. I have done several test flights to find out the exact conditions it occurs and I find it can happen any time there is a sunlight glare hitting the sensors, with either the sun low to the horizon or sun reflection off water. I also found that RTH does not break the complete stop. In any case, S mode will save the day.