[Bug] Child-Tabs can't be closed, indented too much

[nilsbraden]

I got a strange issue:

Somehow it happens to me that a new tab is indented way too much to the right and this tab can't be closed afterwards, except if it is not the last tab on this level. If I open another one the former can be closed but from this moment on, one stays and can't be closed. If i restart FF and restore the session these tabs appear on the first level and can be closed properly.

Has anyone seen this before? Can you tell me how I can start debugging this, is geckoprofiler the right addon for this?

[traxium]

Make sure you don't use Tab Groups.
Wrong indentation is very likely to happen if you disable this add-on, move tabs, and then enable the add-on. But it doesn't cause any errors or strange behavior, after rearranging (dragging and dropping) everything should work fine.

One way to start debugging:

1. Open Browser Console (Ctrl+Shift+I)
2. Press the settings button in the right top corner
3. Check this two options:
   
4. The new button "Debug" will appear in Add-on Manager: