Thanks Jonathan ((@jpantan) for taking the time to collect all those references (the WPMU DEV link appears to be broken). I have reviewed them (taking into consideration @bcworkz caution) and made some adjustments but the problem persists. Unfortunately I’m not a coder so the nuance of the php eludes me. In any case, I can say there is a difference between the child and parent themes, as confirmed by switching between the two. The files however are unaffected by changes.
I’ll continue to fiddle with it.