Need help on photos with Inon UWL Dome len

My first post here after reading you guys for a while but it seems there is no other topics related to the same problem I have.

I'm using Olympus C-5050Z with Olympus PT-015 housing, Inon D-180, Inon UWL100 + Dome. I am having problem with UWL100 + Dome. When I use it at the max wide angle zoom, all the shots taken will have a small dark corner at the bottom left of all shots. With the normal horizontal shots with reef at the bottom, it's quit difficult to spot that but with vertical shots of big blue background, it's easier to see.

The sample here are from my first time using this Inon dome lens in Maldives. Now this problem is still there, I only avoid it by not using it at the widest angle of camera. Is there anyway I can fix this problem? Please advise. Thank you.

I have the same problem with my PT-015 and the Inon dome setup. I usually resolve it by zooming in just slightly. I'm assuming this might be caused by the camera not fitting perfectly aligned inside the housing... but this is only a guess.

I think it's the shade from the dome. You need to place the (For lack of a better name) petals in the 12:00/6:00 position. If it's turned too far, it becomes visible because of the wider aspect or view of the image on the long side. If you look at your shot, a slight clockwise (or a major counter-clockwise turn if it's too tight to turn anymore) twist of the dome would have put it out of the image. I had this problem all the time until I figured it out.

Rand