No subject

at least for me as early as it is right now ;-), I tried the
following procedure to reproduce your problem:

- Image Folder: `ImgTagMoveTest` with images
   - img_tag1.jpg
   - img_tag2.jpg
   - img_tag3.jpg
- With tags:
   [ ]  TagMoveTest
       [x] TagMov1
       [ ] TagMov2
       [ ] TagMov3
  where img_tag1.jpg, ..., img_tag3.jpg are exclusively tagged
  with TagMov1, ..., TagMov3 (i.e., each image has the corresponding
  tag and just one tag).

- Now I create a new Tag, `TagsMoveDestination`,
  using the Right-side bar "Tags/Comments"
  and move, one-by-one, using drag and drop
  TagMov1, ... TagMov3 to `TagsMoveDestination`.

They all move fine and the images keep their association.
So presumably I am testing a different case than you describe
above.
Could you tell me which test I should do to reproduce your problem?

Best, Arnd