Many of those status codes come from the underlying ZigBee stack which I presume the XBee is simply passing through. In this case 0x72 corresponds to EMBER_MAX_MESSAGE_LIMIT_REACHED which determines when it has reached the maxmimum number of simultaneous unicast transmissions. This isn’t a fatal error and should quickly clear as outstanding TX requests are completed. Should be safe to retry any TX that receive this error or otherwise space out your TX to minimze chance of encountering.
I’m not 100% positive that this is the behavior of the XBee. Some of the status codes documented for the TX Status frame do NOT correpsond to status codes from the underlying stack. However, one of the newer status codes corresponds to a stack code for example 0x74 = XBee: Data Payload Too Large = EMBER_MESSAGE_TOO_LONG.
My guess is they do some translation on some of the status codes and pass through other status codes directly.