Do you know? Wifi ac bands permissions are different in different countries and devices.
My samsung smartphone can see only UNII-1 (Lowest) АС band.
But MPWP start АС in auto mode in UNII-3 band.
I was confused until googled info about samsung AC bands. Then i assign manually channel 48 for AC band and all works excellent.
So it is good idea somehow to take into consideration features of attached wireless devices and geo locations.
May be needs additional settings for compatibility or something else.
I read reviews on Amazon, and I see people describes the same issues, but they don’t know that they need just change wifi channel.
AC radio bands are controlled by regulatory authority, and it is actually unlawful to allow software to change it.
If your phone and MPW are in two different regulatory domains, then someone has made a mistake in selling the device! 
Where do you live? The only places I know of that would ONLY allow UNII-1 are all in Asia. If the MPWs sold in those same regions are operating UNII-3, they’d be violating regulations…
But my recollection of these regulations is fairly old and exercised…
Your words are true for an ideal world.
Firmware of my smartphone is original, and language and country set are correctly.
Despite the fact that there is permission for all ranges, the manufacturer for some reason made it possible to work only in one.
This is not a guess or an assumption. Information about this “feature” of devices from the Samsung is discussed in the Internet community. And I guess that many problems with connecting а Wi-Fi arise because of the inconsistency of the bands.
So it would be nice if the average user could easily switch them in case of problems. And for this, first of all, you need to inform the user of this option. For example, to make a magic software of hardware button that switches the ranges, which you need to click in case of connection problems.
I don’t think it is crime ))
Ahh, yes, I see quite a few Issue reports in the Google Android tracker… Without reading all of them, it sure does appear the manufacturers screwed up… if they don’t support the full RD’s allocation, they are not 802.11a,n, or ac compliant and should never have been WiFi certified.
That makes me think (and a lot of the issue reports agree, but not all) that it’s a software defect in Android OS. Check the last dozen or so posts of this report.
At any rate, if WD were to only do auto-discovery within a subset of the RD’s allocation, it might fix you, but it would break others that have the same fault but affecting different ranges.
So that’s like a no-win situation. 
It’s enough to write a note in the web interface http://mypassport/UI/, like: “if you have any connection
problems, try manually to set up the channel number.”
Or make step-by-step troubleshooting wizard.
I sure info about AC troubles must be on “Hello” paper near a wifi password.
