Why don't you try changing the N2400 baud to T2400. BS1 does not have level shifter so these should match (plus the RFID says it will output to any TTL-compatible UART).

So the PB code would be:
Code:
SERIN Rx, T2400,($0A)
SERIN Rx, T2400, tag0, tag1, tag2, tag3, tag4
SERIN RX, T2400, tag5, tag6, tag7, tag8, tag9