This problem is strictly related to what C3 does to restore the main layout of panes. It is a long standing issue, and we haven't been able to pin down what causes it, mainly because it is very difficult to reproduce, personally I have never seen it.
By deleting the information from the browser's storage, the problem can be avoided. With no pane state data, C3 will just load with the default pane layout. Of course this is only a stop gap measure and the problem will eventually resurface.
The easiest way to "fix" this is by deleting all the browser's storage, but that is not always desirable, as you loose other setting which have nothing to do with this. To delete just what is causing the problem do the following.
In Chrome:
- Open Developer tools
- Go to the Application tab
- Expand the indexedDB entry
- Expand the PersistantMap entry
- Click on keyvaluepairs
- Right click and delete the "UI_STATE" entry
That should get rid of only the part that is causing problems, instead of all the settings.
It would be very useful to get a copy of the data that is causing problems, but I just realized that it is quite difficult to copy data right out of developer tools.
I wrote the steps very quickly, so if you need any help finding any of those things just post back.