I'm having a similar behaviour here, running NGCam 7.14 v.2.0 on ArrowOS.I'm sure I'm missing something, but when I take a photo with NGCam_7.4.104-v2.0 in nightmode (maybe in others too) it's only displayed in preview in the lower right for a second and then vanishes. It's also not in gallery. But it's in the DCIM/Camera folder and looks like every other photo. After a few minutes it's also visible in gallery.
But it fails to show any picture (located in the DICM/Camera folder) by using the GCam's integrated viewer anyway.
Nevertheless, taking pictures is still OK, and the thumbnail feature (i.e. showing the small preview at the soft button in the GCam's lower right corner) works fine as well.
When trying to open the image viewer by tapping on that button, the image is shown for a part of a second, than NGCam shows a black screen with the camera's elements above, just as if the lenses were covered. To get back the photo preview on the screen, I have to change the lense currently used.
As far as I remember, I had the same (or maybe just a similar) behaviour testing the trCam afew days ago - which isn't surprising due to the fact that trCam is based on NGCam (as mentioned above).