NR7101 DHCP issue

Hello! Have mounted 2 NR7101 at customers houses. At the first installation after one o to days the router in NR7101 starts to give units in LAN the same IP so their is some problems that it dont remember what IP that it has given to what units IPs to. so to fix that I needed to install a router behind the NR7101 than the problem was dissolved. An yes DHCP is enabled in the NR7101. I installed one in a new site and I get the same problem there Accespoint drops IP gets messed up totaly weird. Same with the first firmware (but it was wery bad speed) upgraded both to 100ABUV4C0 and its the same the routers DHCP is totaly messed up. tried reset but no it does DHCP bananas the only way is to set fixed IP on all things (no solution) or but a router behind. I have installed 4G LTE7409, LTE7480 and they workes lite charm but NR7101 is some firmware mess