I’m really starting be confused, because from the screen you post i really don’t see anything strange about your conf.
Maybe can be worth try to put the ACL rule on the owner, with the recursive flag applied (if you still didn’t try).
As you can see, my ACL rules are pretty simple (in this case im the only one supposed to accesso to dataset), in other dataset i just add 1 or more users allowed only read.
Have you try to connect to SMB providing just the ip of the machine, instead of the full path?
Have you made some change to the SMB service? This is my conf, maybe try find some difference:
Have you already try to connect to SMB with other device, like a smartphone? (for avoid the possibility of some Win client problem, despite you have try some device but if i uderstand correctly only Windows machine)