I have been using RE200 in AP mode for about 2 years without problem, 3 intotal

I purchased 4 more to expand usage in my house ( big house with 2metre walls . 
 

since installing I upgraded all to lates version of software and since then my Wi-fi has been unstable with varying band width, slow on Wi-fi  particularly in video conferencing, loss off upload some time loss of down load , face time , what's app. 
 

what I tried 

band width test , from Mobil phone on Wi-fi 2.4GHZ AND 5.0GHZ 

EACH DEVICE 

then compared with Wi-fi Vai pc same 

finally tested with Cat 5e tester on each connection and then bandwidth test via laptop via cable cat .

and then same with master router (sky) 

sky router stable on wire and Wi-fi.

all RE200 , intermittent in AP mode 

read firmware may be cause ? 
 

please advice 

0118alan