I recently started having connection issues on my network.  Specificly a new Amazon firestick 4K perioticaly looses connection and shoes an error message similar to "network error is preventing connection".  sometimes I can get it to reconnect by power cycling the firestick and others I need to reboot the entire mesh.  I have other firesticks that function properly when this on is offline. also have an e-reader as well as a smart switch that looses the network and needs reset or power cycled to reconnect .  network setup is XE75 as the main in router mode with direct connection to ISP (Fioptics). Ethernet backhaul to 2 additional nodes (X68 and M9 Plus) and wireless backhaul to 3 additional nodes (X68 and 2 - M9 Plus). All nodes have most current firmware. Network optimization in the app shows "perfect".  Signal strength seems good everywhere and the problem devices are less than 10 feet from a node. Sometimes the network seems slower than normal but have done no testing to confirm actual speeds.  Usually speeds are above 400MB which is what I'm supost to get from my ISP.  Any ideas?