[CentOS] Reliable way of having both LAN and WIFI on headless box

Once again I am building a headless Centos 7 box that needs to reliably be on 
both the LAN and WIFI network at all times.  Amongst other things it's going 
to be an AirPrint bridge enabling IPads to print to printers on a different 
VLAN.

I have asked about this before and got a solution working using nmtui to set 
up both the LAN and WIFI interface, and activate them.  However, the WIFI 
link is unreliable. Sometimes it doesn't activate, or after a while 
de-activates.  Sometimes it doesn't even appear in nmtui to enable me to 
activate it.

Can anyone help me with how I can set up a more reliable server.

Thanks

Gary