Correction lost after half an hour on Ethernet NTRIP Master

Hello,
I use simpleRTK2B Pro products, with PointPerfect correction provided by 4G NTRIP Master or Ethernet NTRIP Master.
The application is to get the position of a static object.
Everything works well with 4G NTRIP Master, GNSS is fixed after a couple of minutes. The correction continues for hours, I see the number of SPARTN messages increase about 3 messages every 5 seconds on UBX->MON->MSGPP (Message Parse & Process).
When I use Ethernet NTRIP Master (replacing the 4G NTRIP Master on the same simpleRTK2B Pro module), GNSS is fixed after a couple of minute, but after a half hour, GNNS state change to NoRTK. On UBX->MON->MSGPP(Message Parse & Process), I see that SPARTN meassages are stopped between 1915 to 1920. UNKNOW messages are also stopped. There is no activity on the UART.
The state Led of the Ethernet NTRIP Master is always green.
Ethernet NTRIP Master seems alive : if I unplug the ethernet cable, the state Led turns red and returns green when I plug it.
The only way I found for retrieve correction is a hardware reset (unplug and replug Ethernet NTRIP Master module on the XBee support). Correction works for a half hour and then stop (SPARTN message increase up to 3934 and stop)
This is the configuration file of the Ethernet NTRIP Master :
$$$AS+d=0
$$$AS+1=192.168.0.218
$$$AS+2=255.255.255.0
$$$AS+3=192.168.0.254
$$$AS+4=8.8.8.8
$$$AS+B=115200
$$$AS+N=0
$$$AS+S=
$$$AS+P=
$$$AS+U=
$$$AS+M=
$$$AS+n=0
$$$AS+s=
$$$AS+p=
$$$AS+Z=1
$$$AS+z=pp.services.u-blox.com
$$$AS+Y=ardusimple
$$$AS+y=0
$$$AS+X=0
$$$AS+x=0
$$$AS+W=0
$$$AS+w=
$$$AS+V=
$$$AS+v=
$$$AS+t=
 
I don’t find information on the hookup guide for debug the Ethernet NTRIP Master, do you have any suggestions ?
Thanks for your help,
Best regards,
Bernard