WIZ 1000 server mode get stuck

we use WIZ 1000 in TCP server mode, connection timeout 10 sec, tcp keep alive 20 secs, other settings left at defaults.
It happens occasionally, that the wiz 1000 gets stuck - both ethernet link and ethernet act leds lit constantly, and the unit answers only ping messages, no tcp and no search from configuration utility. Powering the unit off and on fixes the problem.

What to do about it - is it rather faulty unit , to be replaced, or do we have to do something about settings or firmware upgrade ?
Could it be that too dense ethernet communication jams the device ? - it is on public ip address.
The current firmware version is 1.6

I have the same issue. Did you receive any answer ?