Hi Keo,
Thanks for reporting!
We had a few reports about the issues with the Bluetooth stream on some Samsung devices. Mostly, the Bluetooth connection became unstable after the Android security patch updates installation. We released 28.1 Reach Firmware with a fix for it.
But I see that the issue persists for your Samsung Galaxy Tab A7. Did you notice when this issue with the stream appeared on your device? Can you please send the Full system report from your RS2 to support@emlid.com?