ORBI AX RBR 753 Wired to Metal building/intermittent internet/modem issues as well

I have the Rbr752, purchased another satellite after.  with a CM1200 modem. I recently built a wood framed metal building 25’ from the back door of my home. My home is about 2500 sq ft one story on about an acre of property. The metal building is 16x36 with a second floor full walkthrough loft. Electric has been installed in the building, along with one cable line and one solid Cat 6 Ethernet wire. I placed one of the satellites in the building, and have it hooked up to the cat 6 cable, on the main floor. The other end of the cable runs into my home, and is hooked up to my Orbi router. The second satellite is in a bedroom window, directly across from the building, also wired to the router. approx, 30' from the router. Once I wired the connection from the metal building, to the router in my home, the Wi-Fi signal in the building is awesome. I get almost 700-800mbps between the two points outside and INSIDE of the building. The problem I am having is once I am inside the metal building, with amazing Wi-Fi speeds, I lose internet connection unless I am right by the window that faces the house. I am baffled by this because my Wi-Fi signal and speeds are amazing in the whole building, second floor as well. But my phone frequently disconnects from the internet, unless i place it in that window. My phone even says no internet connection.. So how do I have speeds sometimes over 800mbps, through the whole metal building, with no internet unless I place my phone by that window. I can even walk behind the metal building and keep the same speeds. Inside the building, Calls will go straight to voicemail, I can’t send or receive text messages, and obviously can’t get on the web. I have already purchased 500’ of cat 6 wire, to install through my home, and wire everything except for the phones, laptop, and the kids’ game devices. I’m going run new cat 6, and connect to a switch and patch panel through the whole house.. I am learning as I go here, but I am baffled by this. Before I ordered the second satellite, I contacted NETGEAR SUPPORT,  and confirmed that a wired connection in that building was needed for strong internet, due to the building being away from my home and being metal at that.  Again I feel silly why I can’t understand why in a wired situation, I am having this issue.  Yes I checked to make sure the wiring is good, and it shows that the satellites are wired on the GUI and on the Orbi app, so it’s definitely hooked up properly. Thank you in advance for your advice and time.. I thought maybe an outdoor satellite between the house and building but again how to you have 800mbps internet speeds in that metal building, with internet connection that comes and goes, when the speed is a constant???

ALSO, my front yard has very weak connection. Purchase ANOTHER satellite?? the 2 I have should well cover my home and all my property. Maybe put the satellite thats inside the house, more towrds the front of the house instead in the back bedroom, adjacent from the metal building? ANY advice would be very appriciated!!

ANOTHER ISSUE:

also i cannot get my modem to pick up IPV6, and the connection to the OFDM Downstream, connects then disconnects and reconnects daily, (Power-5.6dbmv),(SNR 40.1)subcarrier range 1108-2987. I have the Starting Frequency on 579000000. i only have one splitter, from comcast, no junk. Power and SNR are all in good range. i think..POWER is (-2.9 to -7.7). SNR average 4.1  

Hopefully THE MAN,  Furry,  can give me some professional advice, but ill take it from anyone!! Thank you