Can you provide some self-sufficient source code which reproduces this problem so it is easier for others to take a look?

(In reply to Dominik Stadler from comment #1)
> Can you provide some self-sufficient source code which reproduces this
> problem so it is easier for others to take a look?

XWPFDocument doc = new XWPFDocument();
XWPFTable table = doc.createTable(1, 1);
XWPFTableRow row = table.getRow(0);
XWPFTableCell cell = row.getCell(0);

String expected = "this must not be empty";
cell.setText(expected);
String actual = cell.getText(); //actual is empty
Assert.assertEquals(expected, actual);


//under code work well
XWPFParagraph p;
if (cell.getParagraphs() == null || cell.getParagraphs().size() == 0) {
    p = cell.addParagraph();
} else {
    p = cell.getParagraphArray(0);
}
p.createRun().setText(text, 0);