AC 1900 2.4 and 5GHZ lights flash green, other parties often get “Poor Connection” using FaceTime ,

1.  Are the 2.4 and 5GHZ supposed to be solid green?  They are mostly green but regularly flash off for part of a second. 
2.  When using FaceTime, the recipients often (but not always) get a frozen picture or show "Poor connection".  I can usually see them fine.  This can occur when no other devices are using the router. 
3. When I unplug the modem and plug it back in, it seems to resolve the poor connection issue for awhile. 

Cablemodem is 2 years old.  Using Cox internet with 60MPS download and 3MPS upload. Speed tests generally confirm these speeds.  Cox cable sales representative suggested that a new modem would be advisable. 

Any ideas?  Thanks,  David