Bookmarks bar list horizontal display trouble after update 71.00

Hello
After updating 71.00 portable, the bookmarks of the favorite bar are displayed horizontally, preventing access to all bookmarks available. To get around the problem, I have to create and insert an empty folder as firts element of the list , so they are displayed correctly, i.e. vertically. Already tried to start Firefox with disabled add-ons.
I tried to get the previous version (I backup everything ...) and when update to 71.00 the problem occurs. Strange that it just happened to me.
Any suggestions to fix the problem?