If by OUT you mean "forward", and it is always perpendicular to the vector UP, then NO, you will not encounter cardan lock.
What you are doing is creating an orientation matrix from the UP and FORWARD vectors and applying this frame, which is a fairly common method for moving a camera in space. You do not apply several turns using Euler angles, which may cause the driveshaft to lock.
Note. To create a matrix, you will also need to create a βleftβ (or right) vector from the UP and FORWARD vectors. A good introduction to this is here - note that this example applies rotation to the camera matrix, which is a completely optional step.
Wikipedia has a good explanation of gimbal lock .
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