I went to the NI tower during the maintenance and tuned the camera focus. The image is now good (Fig.1).
Since the image on the NI_Cam appeared out of focus again, I went back this morning.
I thought that the camera had somehow moved, but the image was the same as last Tuesday. Michal suggested that, with natural light, the camera sees through the HR face of the mirror and therefore I had mistakenly tuned its focus on the AR face.
I went back at 16:00 LT to re-tune the focus with the ITF locked. I managed to do so without causing an unlock.
The beam is now clearly visible on the mirror (Fig.1)
Figure 1. I have reduced the integration time of the camera from 15000us to 5000us, so that it is the same as the WI camera. Both are still larger than the NE/WE cameras, that have an integration time of 1800us.
