RS adapter buffering problem

I’m using ConnectPort x8 and XBee adapter. I’ve loaded standard files included in X-CTU into ConnectPort, so data transfer with adapter is via specific port on coordinator IP.
When I set rs parameters as: 2400,8,e,1 and set Packetization Timeout different than 1ms, adapter looses some bytes in frame. Setting 1ms solves problem of loosing bytes, but it’s not very satisfying solution. Frame has about 160 bytes. Has some met such a problem ?

On adapter I have the newest firmware version - 0x1247