I do not really know where to post this issue, probably someone have an idea:
I have 3 PCs, a NAS, a router and of course an android phone.
2 PCs connected with wifi, 1 PC and NAS use lan, my phone uses wifi also.

There are samba shares on the NAS device which are available from all our PCs. All the shares are protected with user/passwd, there is no guest account. I cannot connect to that share from my phone, I tried a lot of different application. There is only one exception:

X-Plore from lonelycatgames.com can reach it, but without user/password. I have no any idea what kind of protocol was used, but the shares can be seen and available without password.

Can anyone explain how is it possible?