Peculiar Results Attempting to Select Tabs in Tree

[GageWilliamErvin]

It's difficult to identify exactly the circumstances under which this issue occurs, but it seems like there is a bug wherein a branch of tabs gets corrupted somehow and all subsequent branches and children are not selectable, i.e., 'clicking' a tab might select a tab further down in the list instead of the tab 'clicked' or not have any effect at all. In spite of this, the path to the tab which is actually clicked is highlighted in the tree. Restarting the browser does not correct the issue.

Version 1.4.8 FF Version 50.1.0 OS Win7 64 MacBook Pro Other Enabled Extensions: Block Site Following is a URL for a PNG image of my tab tree. All tabs in the first two root branches (and their sub-branches) can be selected without problems. Selecting the the third root branch works. Selecting the first subtab of the third root branch opens the fourth root branch instead, the second subtab the fifth root branch, etc. Selecting anything after these has other results. https://drive.google.com/file/d/0BweZA5GGQX5qVzdwODNjbFNHamM/view?usp=sharing