Airplay not show on OpenWrt router oftenly

I just upgrade my openwrt router from 18.06.2 to 19.07.3, all setting are keep, and airplay often not show on this network.
everything is working on before, but after upgrade (router and NAS OS same time...) , my NAS have issue on shairport-sync, therefore i plan to install airplay server on router. I believe the problem does not necessarily case by router OS upgrade.

If i successfully connected to Airplay, all just work fine. but airplay server appear irregularly, about 5 min will disappear (most of the time not show), restart iPhone, router still not working.

I try to using Android phone (running AirReceiverLite) and iPhone connect to Windows's hotspot, the AirPlay server will show up immediately (same result if connect to Android hotspot ) and all working fine.

Same Android Phone (running AirReceiverLite) and iPhone connect to Main router, No AirPlay server will show.

AP's Isolate Clients is disable.

Do anyone can help or know why?

Many thanks!!

Here is my network setup

Main router
running shairplay, shairport-sync (uci config) , shairport-sync (shairport-sync.conf), different port
19.07.3, disable IPv6

AP1
19.07.3, disable IPv6, DHCP

AP2
19.07.3, disable IPv6, DHCP

OMV NAS
running shairport-sync using docker

Android phone (MiMIX2)
running "AirReceiverLite"

mDNS result on NAS:

root@NAS:~# avahi-browse -r "_raop._tcp"
+ veth0a7bb11 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ vethf481966 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ veth24d18b3 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ vethc5e20e0 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ docker0 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ docker0 IPv4 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ enp3s0 IPv6 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ enp3s0 IPv6 485D607CEE22@JVC-AUX-sp                       AirTunes Remote Audio local
+ enp3s0 IPv6 81B51AA14EBF@JVC-AUX-sp_uci                   AirTunes Remote Audio local
+ enp3s0 IPv6 022CB800A173@JVC_AUX_sp_c                     AirTunes Remote Audio local
+ enp3s0 IPv4 020000000000@MiMIX2-79                        AirTunes Remote Audio local
+ enp3s0 IPv4 C5FD214CDD0D@Docker                           AirTunes Remote Audio local
+ enp3s0 IPv4 485D607CEE22@JVC-AUX-sp                       AirTunes Remote Audio local
+ enp3s0 IPv4 81B51AA14EBF@JVC-AUX-sp_uci                   AirTunes Remote Audio local
+ enp3s0 IPv4 022CB800A173@JVC_AUX_sp_c                     AirTunes Remote Audio local

running " avahi-browse -r "_raop._tcp"" on Main router can get same result.