I'm not sure if you read the whole 3 pages worth of information on Auto-wake-up on break, but it'll take a little more than flipping a bit.

The transmit side needs to send the right character (0), or a Break sequence, to wake-up the PIC or you will loose at least the first character and get a framing err (FERR), and possibly a buffer overflow (OERR).

The second character can also be lost if time is not allowed for the oscillator to stabilize.
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