Not all folders (meta tag folder) are shown in item search (with possible explanation)

In the document search filter bar (right side of search) only 8 or 9 folders are shown even if the folder category is expanded. I made 12 folders and only 8/9 are shown. it is not clear which ones are omitted, makeing new folders and removing them seems to randomly only show a subset. The folders are correctly displayed when you are in edit mode (then there is a combo pull down menu where all folders are listed). But in the the side bar where it is not a combo but a list of items they are missing.
If this is a bug and not a wrong operation of me I would say this is a critical bug.