Checkbox in Excel is affecting a non-linked cell

I have a column of 67 checkboxes in an Excel sheet. All checkboxes link to the cell they are placed upon, so that TRUE/FALSE is written to this cell. However three of my checkboxes are also changing the value in an adjacent cell, and I cannot see how.

Interestingly, it changes the value of the adjacent cell, but the checkbox sitting on top of that adjacent cell doesn't toggle. Any ideas?