I had given some thought to proximity of xtal and serial wires but was space-contrained on my breadboard. Also because I am using a 3-pin resonator rather than a crystal, it's a bit awkward to place close to the xtal pins and I have run it out to a spare section of the breadboard.
I might rewire on a bigger breadboard and see if I can reproduce the reboot issue.
Your board looks great Jack!