Ha! No, for once, I actually now understand what you are saying, as I was forced to do enough research and study to try and figure out a way around our problem. Yes, I did try both setting static IPs on the individual computers, and when that didn't work (with AC), I tried the router reservation attached to MAC addresses (always being careful to restrict the DHCP slots to those outside of the reserved range). AC still wasn't satisfied, and kept "forgetting" and losing the connection to the main PC, despite my typing the exact numerical IP address path to the AC db into each computer.

Finally (we had to get our medical work done!), I replaced the Win10 main PC with the Win7 PC and all was suddenly well and calm, as if a Rossini-like thunderstorm had passed!