Using Linux Mint 18, WPS alpha 21.

To reproduce the bug, follow these instructions.
Open up a new Presentation file.

Switch to Outline view (not Slides) and hit enter once to create the first non-title slide.
Type in a letter (the header for that slide)
Press enter and tab and type in a second letter (first bullet point)
Press enter and tab and type in a third letter (first sub bullet point)

It should look like the following (where "-" represents the first bullet point and ">" represents the sub bullet point that is under the first one)
D
- D
> D

Move the caret to the right of the letter in the first bullet point ("|" represents the caret)
D
- D|
> D

Press backspace once: the letter is deleted
Press backspace a second time.
Expected: bullet point is deleted and caret is moved to the right of last letter in header
Reality: nothing is deleted and the caret does not move.