Thanks for your quick reply. Our routers works with 4G mobile internet (we have over 50 pcs)
Before FW upgrade the Network was set to WAN (it does not exist WAN1, only WAN, WAN2, WAN3)
After FW upgrade to 1.11.3 the Network is set to LAN, which gives afterward erroneous IP address to the DDNS.
I've done it on several RUT240 routers with FW1.10.0 and gives the same result. I had to correct it manually to Mobile (PPP).
I think furthermore that this is an issue which must be corrected.