Help needed with trimming solids with chamfered edges

Hi there,
Really new to Rhino here, just started two weeks ago so please bear with me if this is a really simple question.

I’m trying to draw the base between these two solids

First, I extruded a curve all the way past the right side.

Then, I extruded the extrusion created from step 1 upwards by 0.5 cm.

Now, when I tried to trim the new extrusion using the right side as a cutting object, it deletes my entire new extrusion instead of only the outer side.

Could you please teach me what I am doing wrong?

These are the object properties of the right and left sides, as well as the base.

Thanks for your time! Much appreciated :slight_smile:

PS: I have tried to do this in my girlfriend’s Rhinoceros on windows, and it is still unable to trim how I wished it to.

are those solids really solid? to me it looks like the circular cutouts protrude the side.
otherwise, post the model so others can take a look at what’s wrong