I've noticed WP8.1 very temperamental about security settings on Wifi networks. I was having the laggy lock button issue, but only at home, not on my work's WiFi network and not when WiFi was off. I was just spit balling trying to troubleshoot the issue when I discovered changing my security from WPA2 to WPA seems to have, for now, solved the issue. Also, turning off Wifi Sense has been reported to help in some scenarios.
Hopefully this bug gets squashed, or if anything, it could be firmware related and could fix itself on the official release.