Interesting thing: if I leave the house and return without having used the tablet on another wifi network, it immediately is up and running on my home network when I get back.
If I leave the house and use the tablet on another wifi network, when I return it says my home wifi "is known to Android but signal is too weak/too far away to connect"
I have gone thru the usual procedure of changing channels etc.
Of course resetting the router results in an instant connection. But that shouldn't be necessary (ha ha).