When you use Alt-Enter to fill in multiple cells, it's only working on first
time edits (see [A] below). If you want to fill in existing text [B], you first
need to tell Calc to "wake up" ;-) by moving the cursor [C]. Calc should always
fill in the text, when you press Alt-Enter.

[A] This is working:
1) Select three cells A1 to C1 with Shift-Cursor Right and press F2 to enter text.
2) Enter some text ("example")
3) press Alt-Enter and the text is put into all three cells

[B] This isn't working (the bug):
1) Enter text ("bug") into A2 cell only
2) Start from C2 backwards to A2 to select cells (Shift-Cursor Left) and press
F2 to edit
3) Press Alt-Enter ---> and the text is NOT filled into all three cells

[C] Workaround (quite annoying):
1) Enter text ("workaround") into A3 cell only
2) Start again from C3 backwards to A3 to select cells (Shift-Cursor Left) and
press F2 to edit
3) Now move cursor left and right while you're in the edit mode of the cell
4) Press Alt-Enter ---> and the text is now filled into all three cells