I'm using RFID API3 and Barcode Scanners library together on the same device. When performing firmware update everything goes fine until RFD8500 is restarted. At that point I shut down both connections to the device and connect anew. At this point, RFID library throws any of the two exceptions and connect fails:
OperationFailureException (statusDescription: RFID_API_COMMAND_TIMEOUT; vendorMessage: Response timeout)
OperationFailureException (statusDescription: RFID_API_UNKNOWN_ERROR, vendorMessage: Unknown error) while connecting.
After a few retries though (1-5), it succeeds. I also tried shutting down RFID connection before firmware update starts, but got the same exceptions for the first few retries. I saw in the release notes for RFID library 220.127.116.11 (the very same that I'm using) that RFID_API_UNKNOWN_ERROR was fixed, but I'm still getting it.