This one beats me ...

I have tried to make this a solid using boolean commands but there is a flaw somewhere so all I can get is a joined surface. I have spent hours searching and did find some flaws but the critical one escapes me.

I need some help.

Another bit ... I can't make the band on the lower face fillet its edges. I want to match the upstanding band on the upper surface (more or less)

This is a rebuild of an older model that was a good solid but I'm getting nowhere with my modifications.

thanks,
eric