When you write in a mathfield:
\lbrace 2x\mid x\in\mathbb{R} then click enter
and then }
and afterwards you revert to the latex by ESC, you see this:
\lbrace 2x\mid x\in\mathbb{R\rbrace}
What would have been expected is this:
\lbrace 2x\mid x\in\mathbb{R}\rbrace
Upon examining it seems that although one closes the \mathbb{} with a right curly bracket - it includes everything that comes after it inside as an argument for the mathbb.
When you write in a mathfield: \lbrace 2x\mid x\in\mathbb{R} then click enter and then } and afterwards you revert to the latex by ESC, you see this: \lbrace 2x\mid x\in\mathbb{R\rbrace}
What would have been expected is this: \lbrace 2x\mid x\in\mathbb{R}\rbrace
Upon examining it seems that although one closes the \mathbb{} with a right curly bracket - it includes everything that comes after it inside as an argument for the mathbb.
To wit: