Tags disappear when I check this box

In my quest to find a way to strip the ID3v1 tags from all of my .MP3 files, I finally realized MP3 Tag could do the job. Trying to make sure I would be doing it in the correct manner, I went to Tools -> Options -> Tags - Mpeg and starting investigating what all the checkmarks controlled. When I checked the control for Read - APE, I was surprised to learn that none of the tags appeared. When I unchecked that control, all the tags reappeared. Why does checking that box prevent the tags from appearing?

After configuring MP3Tag to remove only the ID3v1 tag, I selected one file, right-clicked the filename, and selected Remove Tag. In the Tag column, ID3v1 is removed. When I save the file, the tag is restored. Why does this occur. How can I remove the tag if saving the file brings it right back.

Ultimately, what I need to know is how can I remove the ID3v1 tag only from about 7000 MP3 files, en mass? And, I would like to not modify the time and date stamp. Is there another program capable of doing this? Or can MP3Tag do it using a procedure that I am not aware of?

APE tags are read with priority over ID3Vx tags. So if you have APE tags in a file but just one field is filled, then you see nothing more than just this field, regardless what other data still resides in other tags.
Load one of these files with APE reading switched on and open the extended tags dialogue (Alt-T). I would assume that you have replaygain fields in APE tags.
If you don't really need them, delete APE tags and never write them.

You've probably saving of ID3v1 enabled at Tools → Options → Tags → Mpeg.

I do have replay gain information from MP3Gain saved in the APE tag. So that information needs to be retained.

Yes, I did have the option checked for saving ID3v1 checked. While checking and unchecking the boxes in search of the "correct" settings, I left it checked and did not see that.

I have a SanDisk Clip Sport Plus Player that has a problem of duplicating the artist name when I list the files by artist. Let's say I have ten files by a particular artist. Eight MP3 files appear under the first artist name listing and the remaining two files appear in the duplicated artist name listing. There is no difference, whatsoever, in the tags for those ten files. But, the player finds something different about them that makes it divide the files between the two listings of the artist name. This occurs with some artist names but not all. This morning I found that Winamp has a feature in which I clicked on the Winamp Menu, selected View file info... and I could see the incorrect data on the ID3v1 tab that I had previously edited in MP3Tag and was viewable on the ID3v2 tab. I was confused why the ID3v1 data was wrong when Write ID3v1 was enabled. I had never disabled that until today. Is there a way to get the ID3v1 data and ID3v2 data in sync with each other so there are no differences between them? I feel that is the problem why my SanDisk player is dividing some files under two separate listings of the artist name.