Pasting formatted tables from Excel into other software - issues

I am copying and pasting a large table, with lots of cells merged into, headers for combined rows and colums, with lots of coloured and formatted cells.

When it is pasted into Word or Excel, the first 20-30 rows are OK, but then after a while, mid-row, the colour formatting (but not the cell text contents) becomes displaced a two cells to the right.

The colouring then corrects itself further down the table, but then drifts in and out of alignment.

I think it may be an issue with the merged cells, particularly in the case where if they weren't merged then the content of the cell is wider than the cell, so requires wrapping - but this does not appear to be consistently the issue.

I have tried unmerging everything and allowing columns to autofit to full width, but that does not resolve... it had been fine until around March 2026 - was there an update around then?

Any suggestions welcome.