Is XBee SB6 set to transparent mode have a problem with RTS flow control?

I have Xbee SB6 in transparent mode utilizing RTS flow control for the receiver. I am seeing bytes not coming in as they were sent. Bytes are delayed drastically at times, such as a second or so. Wireshark shows 10 bytes sent. I receive 6 then a significant delay causing my receive routine to time out thus asserting RTS again and then 4 bytes come in as observed with a scope. Is the module “hanging” on to bytes? Some buffer flushed when RTS is asserted again? Are 4 bytes always “held on to”? It says in the manual that 4 bytes may be sent after RTS is asserted. So now I wonder if it is holding onto those bytes. If I extend the timeout the bytes still don’t come in until after RTS is asserted which makes me believe there is a problem with the receiver handling RTS flow control.