I have a problem extruding curved surface.
When a surface included curve and we decide to extrude it further, the curved segment will generate a new curved surface.
It doesn't take long after that the solid starts including some naked edge and will become unusable as a solid.
Yes, we can unjoin surface, delete one of them and rejoining the model, but this it incredibly time consuming on complex model.
Here is a video of the operation.

https://recordit.co/QrxsG57tks

1) Create box
2) Filet edges
3) Extrude top surface
I'm using Beta V5.0 2023-APR-08

I have the same than your figure...

Hi Fran6, yes that's normal behavior currently.

It's on my list to do some work to make extrusion type surfaces merge together, currently only planes merge together.

- Michael

But before the fix Just copy move the top face rounded and extrude it!
Not a big deal! :)