I think I figured it out when I experienced a repeating crash in the drop down control in the network settings, and then looked at the crash report, there was something about localization in the backtrace, so I removed the file in an attempt to fix that and after a logout/ login the weird lag went away too. In my case the file had the value for UTF-8 and something in Tahoe’s text system goes into a loop when that file is present. I’ve had the same file for ages because it fixed a problem with pbcopy/emacs interaction. I wound up working around that issue with an env var once I realized that the file was causing issues.