EX6000 not reaching speeds and wireless devices keep disconnecting?

Recently just moved into a bigger house and 1 room on the 2nd floor at the very back of the house gets poor wifi signal from my Netgear Nighthawk R7000p, so I purchased the EX600 AC750 Dual Band WiFi Extender and connected via WPS but I'm getting consistant speed drops from anywhere to 6mb to 25mb on 5GHz but as soon as I go downstairs near to the Nighthawk R7000p and connect to the actual routers 5GHz signal I'm getting my speeds I paid for (100+mb) and all wireless devices connected to the EX6000 keep randomley disconnecting all the time but all the lights on the EX6000 stay green so not sure what is casuing that disconnection problem? I brought this wifi extender because it has FastLane technology but it's clearly not very fast at all considering it can handle speeds upto 750mb so do I just need to get a stronger wifi extender to hit my normal speeds or is this product faulty?