XBee Pro Series Throughput Issues!!!

For a serial RS-485 wire replacement, will XBee Pro achieve error free throughput or what is the max throughput achievable?

Why I asked is because I was running a simple loopback tests with two Series modules on RS232 adapter and noticed bad packets. Scenario 1 both modules sitting side by side and Scenario 2 the modules are 5~6 metres apart. Though the bad packets count are not a lot like 360000 good ones and 78 bad ones but what’s the possible causes of this drop in packets?