UPDATE 9/9/2016: To my knowledge, this reset caused by changing FPV Frequency has not been fixed. However, I don't think it is the cause of flyaways. Recent firmware updates have reduced the occurrences of flyaways, some possibly caused by a failsafe which drops the quad into manual mode which causes a momentary reset in-flight and changes throttle and control response. The following firmware combination I'm running, recommended to me by Hubsan, seems to work well, and I do not encounter the failsafe into constant manual mode. The quad reset from manually cycling through FPV frequencies still occurs, but doesn't appear to be the cause of reported flyaways.
Good firmware combination (TX, LCD, RX, FC, respectively):
V4.2.8
LCD V1.3.2
H501S V1.2.3
V1.1.17