Thanks for the info & help
Lionel quickly responded to my email today and said to send our Base3 in for warranty repair. 6-8 weeks turnaround so we will send it in when our club shuts down for the summer. I managed to improve the Cab2 response enough so we can run on the Base3 until then.
Antenna boosters were no help. I got a Sunhans Signal Booster amp from Amazon. No risk 30 day return, very pleased. The Cab2 to Base3 operational range is now >40ft through a brick fireplace wall at my house. Better than I ever got Cab2 to my Base2. The Cab2 out of range light flashes a quite a lot outside 15ft. All commands are still getting through. You have to be well within 15ft when you power up the Cab2 for it to find the Base3.
I always use a wifi analyzer app to assess the situation, try different channels, and stay off my router's channel