Problem after adding TurboSmooth modifier

[julia.stadler]

Hi,
I am starting my journey with modelling.

I'm using student version of 3ds Max 2021.

I'm trying to model a tank's turret and I have problem after adding TurboSmooth modifier. Some black artefacts occurs in one place (like on the attached screenshot). I guess it's just my fault and I made a mistake during modelling it - these 5 egdes connected to one vertex don't look good. I was searching the internet for similar problem but didn't find anything.

Generally I don't really know how to connect it properly without loosing the smooth transition from box to cylinder - it's basically 3/4 a box and 1/4 something like a cylinder.

Do you have any idea how to fix it? Tips appreciated 🙂

[julia.stadler]

I added a vertex (under the previous vertex with 5 edges) and connected an edge from "cylinder" to it - i created additional polygon at the focal point. This new polygon looks a bit strange, it looks like it was made of two triangles but it's not. However a mesh with Turbosmooth looks fine (I'm before chamfering the edges so it's not the final shape).

Can anyone tell me if it's a proper way to fix it?