bundle 3.6.2_en-64bit opens too many files on Linux
After a while (if you visit many-many pages) the Tor browser starts misbehaving - can't save files, difficulties with loading/displaying pages, and eventually all fonts (i.e., all text) suddenly disappears from pages and menus as well (except for a leading underscore ). You get errors on console by some shm*() function (cannot recall name correctly) complaining about too many open files and lsof indeed shows bazillion files for the Tor firefox in directory tor-browser_en-US/Data/Browser/profile.default/thumbnails/ mostly in deleted status. Clearly unexpected behavior.
One workaround is to sigterm the browser with kill + pid and when you restart recover all tabs etc. Firefox also has docs on disabling thumbnail collection or usage altogether which should work (have not tried it). I decided to replace the thumbnails directory with an immutable file and have not seen the bug since.
Saw this with the latest 3.6.2 but also with earlier ones.