My bookmark folder names keep changing, sometimes when I make a new folder it will change the name of other folders to the new folder's name, how do I stop this?

I sort all of my book marks into folders with subfolders. Sometimes, for reasons I haven't figured out yet, when I create a new folder or subfolder other folders names will be changed to that same name. Why does this keep happening & how do I get it to stop? This has been happening to me for a while even though I have installed newer versions & updated them, is this just a bug with the newer versions of Firefox? For example, I had a folder with my husbands's name, in the bookmark menu for all his ...I created a new subfolder called phys ed in my education folder ...my husband's folder was renamed to phys ed, also.