Erel, Check out the logcat. Do a search for java.io.IOException: [JSR82]. I get this Error once in while. Maybe for every 6-10 attempts. I use 3 attempts to make sure I close the Astream or else Unpair/Pair is required. If first attempt does not close the Astream then 2nd will and with 100% of the time will close it successfully.
B4X:
Dim x As Int
For x = 1 To 3
If Astreams.IsInitialized Then
Try
Log("Attempt " & x)
Log("Astream.Close")
Astreams.Close
Log("Serial1.Disconnect")
Serial1.Disconnect
Exit
Catch
Log(LastException.Message)
End Try
End If
Next