@KuroYami 

The way to resolve this is to configure Deco mesh to run in Access Point mode: How to set up Deco to work in Access Point mode

In this configuration, your ISP router will provide IPv6 addresses, Deco mesh will just transmit them without interference.

  @Alexandre. 

Yes, i know this works, but i rely heavily on the address reservations function of deco for my home nas. my isp's router doesn't have the static dhcp server function, oddly. my nas and all my network devices will be turned off for the night, so i don't want my nas' ip address to be different everytime i boot them up for the day.

  @KuroYami 

This is truly strange for router to miss such basic functionality. Can you share brand name and model number of your ISP Router?

Also, while it is really what I don't want to recommend, but if it is only NAS, and Deco runs in AP mode - you can configure static IP address on NAS. 

  @Alexandre. 

ugh... i can't share the link. a simple search on "maxis huawei router" will show you.
i've checked on huawei's site and it should have it, but i just can't find it albeit it has the exact same ui for every other function, except the one i want is missing. i can't share the link here, a simple search "huawei router address reservation" will show you.

well, i'm trying to not make it static on the nas, its not really the best practice. i'd rather just stay on ipv4 since the absence of ipv6 doesn't affect me for now. but i would really love to have it if possible.

and the deco's built-in function like new device alert and the parental controls will be gone on AP mode.