I recently replaced a VR600/AC1600 with a new Archer VR2100 and I am now experiencing instability on the wireless link.  At higher signal strengths this is not a problem.  However I have been used to the VR600 working reliably in our upstairs bedrooms.  With the VR2100 router both my Laptop and my Android data-pad the 2.4GHz channel connects significantly more slowly than to the old VR600.  If I leave either of these clients running for maybe 10 or 20 minutes the 2.4 GHz link is dropped in favour of the 5GHz link even though the 5GHz link hardly connects.  The router shows 7.4 db Margin on the downlink and 6.2 dB on the uplink

My nearest neighbour is at least 60 metres from my house and usually I can't even detect a signal from any of their routers.  Occasionally I can detect signals from local buses that pass the end of my property, but the signal is very poor.  The Android WiFi Analyzer shows a signal level of somewhere around -70 to -75 dBm for the 2.4 GHz signal and something below -80 dBm for the 5 GHz signal.  

As a mitigation for the poor WiFi stability I have turned off the 5GHz wireless,  This gives more reliable wireless access, but it still drops outs several times per hour.  However it usually reconnects afer a few moments. 

I guess I could install a repeater which hopefully would give me a better signal strength, but I never needed one for the old VR600/AC1600 based system.  The overall propagation distance between the router and my working space is less than 6 mteres and there is only a wooden floor and a lath/plaster wall to block the signal.