New Varia RCT715 close proximity lines curved at edges.of image/video.

As per title,  I have a new Varia RCT715 and I've noticed close proximity lines are curved at edges.of image/video. This results in distortion of detail towards the edges of the image. It looks like the image wants to curve into a circle at the edges (see lhs of attached image, the curtain edge and window frame appear curved not straight as they are in reality). Has anyone else experienced this?