I have 3 x XE75 Pro on AP mode. The main unit is connected by ethernet to the router, the 2nd device is connected to the main device by wireless backhaul and the 3rd device is in the outhouse connected to the 2nd by ethernet. I have no issues with the 2nd or 3rd devices, but any time my phone or tablet is connected to the main device wirelessly I have no internet access. If I change the settings for my phone or tablet to only connect to the 2nd or 3rd device then I can access the internet. I also have other devices (Sky Q box, home assistant on raspberry pi etc.) connected to the main device via an ethernet port which have no issue with their internet connection, so it seems to me that the only problem is with wireless connections to the main device. 

Any help/ideas would be most appreciated.