you can see the sticker , the ext pin provided a 5V input pin. the ext Pin 3.3V only can output.
could you try to use baud rate 115200.
@dsrc12 thank feedback. we will fix this UIFlow bug as soon as possible. about the BugC Arduino example compile problem . you could trought clone the laster version lib to solve it.
clone the library , then replace files to the Arduino lib path
@jirivanerka Those Pin provided user to design electronic circuit. so default they not connect anything. you can solder they connect to anywhere.