Help 3D Text & 3D printing

when trying to etch 3D text on to a surface it appears as if the centre holes of text ( i.e. 'O" ) dissapear . is this normal or will it effect printing ???

Heal the face of the ‘O’
Use the Line tool to retrace one edge, endpoint-to-endpoint, and the face will reappear.

Dear Sir The Beer’s are on Me !!! Thank
you so much