I am using Firefox version 55.0.3 on a 64bit, windows laptop. I have bookmarks tool bar with some folders containing bookmarks in them. In the last 2-3 weeks, I run into an Intermittent problem with displaying the content of folders in bookmarks toolbar. Sometimes When I click on these folders, the list of bookmarks in them is not displayed, subsequently, I can not click on the bookmarks that are placed within these top folders. When I close Firefox , restart it and restore the previous session it works, ( clicking individual folder in the bookmarks tool bar, shows the content of the folder (bookmarks) and I can select the desired bookmark). Unfortunately this problem repeats frequently and I have to close, restart Firefox, in order to select other bookmarks. Please Advise,

R. Asayesh