AX6000 EAX80 Wifi Mesh 6 constantly unstable

I posted about this problem a couple of days ago and seem to be getting no where. Here is my issue. I purchased a EAX80 and set it up over the christmas holidays. Setup went smoothly pairing it with the downstairs router. I moved the extender vertically so now it sits upstairs but not too far from the router. I have an ethernet cable plugged from my machine to the extender and it worked superbly! 75 MBps and constant connection. However over the weeks now it has slowly got worse and worse. The connection dropped to 50 MBps at best and the connection is unstable when I when I ping/strace command (constant time outs) I have to literally reset the extender daily to resolve this issue which does not seem to be fixing the issue. The longer the extender is on the worse the latency gets. The router is brand new from talktalk and the internet speed (when ethernet plugged) is constant 75 MBps. Help me anyone, my kingdom for a reliable extender.