I found one issue in Inspect that could explain the problems we sometimes have with it: The db tab remembers what watches you've added, and those are written using pr-str to the browser local storage. Unfortunately, pr-str is not symmetric with read-string, and writing a transit type this way (e.g. Fulcro tempid) causes the read-string to throw an exception. I've wrapped the read-string in a try/catch that will clear these (which are probably useless to remember anyway). I have uploaded the fixed Chrome version to the store...should come out within a few weeks. In the meantime, you can always just Inspect the inspector, and clear local storage, or reinstall the plugin.

I'll upload the release zipfile to the Releases in the github repo, if you want to manually upgrade. Version 3.0.5