Probably not, because it some Fx-related (I have Tree Style Tab and see same thing with this addon on browser start). If you use Tab Session Manager try disable "Save the session then window was closed" because it triggered on open all new tabs. Also you can setup dom.script_loader.bytecode_cache.enabled;true on about:config page.
Also see https://bugzilla.mozilla.org/show_bug.cgi?id=1396364
Workaround for this bug: just not have too many bookmarks in subdirectories.