I just found out that several of my Items were not assigned to the Tags because the Tags were formatted as Bold.

Steps for Bug1:

1. Create a Tag “BoldTag”
2. Go to the Tag Grid and make the “BoldTag” Bold.
3. Create a new grid “BoldTag” with Grid Source “#BoldTag”
4. Add items to the “BoldTag” grid => Items are added to the grid(!) but are not assigned to the “BoldTag” Tag

Bug2:

I can’t remove the formatting (Bold) of the “BoldTag” Tag in the Tag Grid (by using the B button).

p.s. It helps a lot to be able to see the formatted Tags in the Tag Pane.  However, the Items may not be assigned to the Tags in this case (see Edit below).

EDIT :
For some Tags, I was able to remove the Bold formatting by unselecting the WYSIWYG Editor and deleting the bold html codes. However, I am not able to delete italic and blue formatting because the italics and blue html codes are not visible!?

For other Tags, I am not even able to remove the Bold formatting because the bold html codes are also not visible for those Tags!?
(They are also not visible when checking "show html codes").

Note:  It appears that for the Bold Tags, which do not show the html codes, the Tags are recognized, and the Items are properly assigned to the Tag! (Very strange....).