STK500.getsync() : not in sync: resp=0x00

[jinwook4217]

while uploading hex file to 'Arduino Uno CH340',
error Can't open connection to MCU occured.

Two out of 30 get this error.

However, it worked fine when I used another app that uploaded hex files.

get log message

recv timeout.
STK500.getsync() : not in sync: resp=0x00
recv timeout.
STK500.getparm() : (a) protocol error, expect=0x14, resp=0x41
[ 09 - 06 18:55:20.888  825:   849 D/             ]
DpmQmiMgr areAllIfaceActive
recv timeout.
STK500.getparm() : (a) protocol error, expect=0x14, resp=0x41
recv timeout.
STK500.initialize() : (a) protocol error, expect=0x14, resp=0x42