i had an mpc file (idv1+ape2 tag) with a title that had two whitespaces in a row and after making it manually 1 whitespace, the ape2 tag was deleted. (i have all fields selected in options-tags-ape)
and i think theres also a bug concerning the display of the tag size. it grows after every saving, even if u save without a change, and if you refresh the view it shows the real size again