One reason QP may put asterisks in a cell is because the cell is too small to fit the formatting. For example, if you try to put the date, formatted as "Sunday, March 5, 2017" in a small field, you will just see asterisks. Double-click on the column letter at the top of the column, and the column will expand to fit the data.
In Settings (Tools | Settings | Application | General), you can choose "Fit-As-You-Go" and cells will expand if you insert something too large in the them. I usually leave this unchecked, so that I don't change the spreadsheet if I insert data in the wrong cell.
Besides the Help file, a full-length PDF book comes with the software. It is under Help | Reference Center, User Guide.
I have personally not found WP X8 to be buggy or have problems.