how many pilots are using the original mini sd card that came with your Spark . i read a post that suggested that a bad or slow sd card creates a bottleneck when writing to the sd card and that causes the video to freeze or loose connection to your phone using OTG or wifi but you can still control your spark from the RC . this has happened to my spark . i am using the original sd card . what i have been doing is after every flight i restart my phone and that seems to help . the other thing is putting my phone in airplane mode for no interruptions from emails and calls .