New update for my QNAP. I've recompiled the firmware, then installed the patched wsdd2 package (wsdd2_2022-04-25-e37443ac-3_aarch64_cortex-a53.ipk), rebooted the router and now 48 hours later it is still working. All Windows machines can access the shares and they don't disappear.
If anyone wants to try the package I can upload it.
One glitch still remains though.
I had to restart the WAN6 interface (because of IPv6 issue) and the shares disappeared.
@Lucky1 can you test this scenario if you have IPv6.
Restarting wsdd2 recovered them. So for now I continue watching and will report if I find anything else.
for me ipv6 triggers a reload & it seems to work fine after that
this is one of the ways to make it fall over
but now seems to work
I'm not sure it fixes everything or 100% but it seems to 98% where we had 2%
1 Like
I've taken another approach to this.
Now I've simply compiled this OpenWrt PR from GitHub.
I've applied it as a patch to my local repository before compiling the firmware for my QNAP. This way the patch fixed wsdd2 package is built-in into the firmware image.
Finally It's working as it should right from the boot. Running for 80+ hours.
It's fully operational (nothing disappears anymore) on all Windows PCs and even on Android phones (I use Total Commander for Android with its LAN plugin to access SMB Windows shares).
I have just been compiling wsdd2
change line in source recompile
make sure output code has changed
but i do like the patch better 
Probably I made a mistake previous time when I compiled the patched wsdd2 package. I've compared the checksums of the old ipk file and the ipk after the patch but they were the same.
Now after recompiling the whole firmware with the patch applied to my local repo the checksums of the old and patched ipk files differ.
1 Like