Can't correctly position cursor in mail on el capitan

This is a really strange one. When composing messages in Mail, if i try to re position the cursor to edit text already entered it will not position and instead stays at the end of the line. I can't select text either unless I select all.

I can manually use the arrow keys to go back, although the cursor itself does not move, so I need to count the characters as I press the arrow in order to make changes. It's kind of counter productive.

I've never seen an issue like this before.