[Steps]
1. Create an Impress doc.
2. Apply "Title Slide" layout, and type a paragraph into the text-box.
3. Select the paragraph, press "Add..." button in "Custom Animation" bar in
"Tasks", and apply an animation to the paragraph.
4. Put the cursor at the end of the paragraph, press ENTER and type another
paragraph.
5. Select the second paragraph and operate stpe 3 again to assign an animation
to the second paragraph.

[Result]
The animation is assigned to the first paragraph again. And when playing the
slide, the second paragraph doesn't have animation while first paragraph has two
animations.

[Additions]
You have to quit the edit mode after typing the second paragraph and get in edit
mode again, then you can assign an animation to the second paragraph.