Wifi repeater/extender/bridge - DHCP through relayd problem

Hi, I have LEDE 17.01.2 installed on my Belkin F5D8235-4 v1 and configured WiFi repeater/extender/bridge to my modem (DHCP server) according to this guide https://lede-project.org/docs/user-guide/relay_configuration . I have a problem, that sometimes my clients on LAN or WLAN on LEDE router won´t get IP address. Example: I connect my NB via cable to router, I get IP from DHCP. I release and renew IP address and now I get nothing. Or I set static IP on my NB, then I change to DHCP and I get address. Then I change back to static and then back to DHCP and I get nothing. Same on other notebook. On phone or TV I sometimes get address on first connection after router reboot but after that nothing. Thank you for help.
Edit: I am doing all configuration via LUCI as I am beginner, so please take that in mind.

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