On a fresh 4.8.1 install, I have enabled Samba with two shared folders.
After I enabled Tailscale and approved the routes, the shared folders became unaccessible from my network and also remotely.
The network shares only works randomly under Windows (sometimes accessible, sometimes not), and they never works using file manager on my phone.
As soon as I stop Tailscale, everything works again (locally and remotely).
Everything was working fine with this setup on firmware 4.7.14.
I am terribly sorry, I just discovered that, completely unintentionally, I added an underscore to my netbios name and that was causing the problem.
Thanks for your time looking into this, much appreciated.