The percentage of ownership at the top of the T2125 goes to two decimal points and is the result of what you enter for the percentage owned by others at the bottom of the form.
The problem is that the top percentage has two decimals places of precision while the bottom allows for four decimal precision. When efiling after using all 4 places we have found that the return gets rejected as it does not add properly.
The fix, I believe, is to have the precision match in both fields.