What does Err:520 mean in a cell?

I have a spreadsheet that links to an external spreadsheet. It worked fine in 4.1 and earlier. However, in 4.2.0-2 one cell, linking to a cell on a specific page in another sheet, fails with ‘Err:520’ if the other sheet is not open at the time the first sheet’s links are updated. Several other cells in the first sheet link to other pages in the external sheet and work correctly. There are no apparent errors in the other sheet, and the link is created by copying the cell in the external sheet, then using Edit-Paste Special-Create Link as for all the others that work. The update works correctly with no other changes if the external sheet is also open in LO at the time of the update. Very annoying - it’s time to downgrade back to 4.1.

Error Codes in LibreOffice Calc

520 Internal syntax error Compiler creates an unknown compiler code.

Please can you show here the formula with the error.

This formula works: {=‘file:///C:/Users/Mike/Documents/Budget/mjbbooks2014/stocks14.ods’#$CVX.G2}

This formula does not: {=‘file:///C:/Users/Mike/Documents/Budget/mjbbooks2014/stocks14.ods’#$IBM.G2}

Formulae are in adjacent cells, linking to pages in the external file. The ‘IBM’ link works if the stocks14 file is open.

In the stocks14 file, the cell linked by the formula is a sum of a column on the page, such as: =SUM(E12:E201). There are no obvious errors in the column. Now is in 4.1 too.