Strange behaviour of solid-tools trim action

So, i have a low detail house model, with simple holes for the windows cut out.
Now i want to add detail.
I created a window frame, which i now need to cut out of the wall around the window.
So i use trim from solid tools as follows:
I made a copy of the window frame and joined that geometry via the “outer shell” command.
Using that outerShell group anywhere on the test-wall in the attached file, i can cut out as desired.
But placing it exactly over an existing window- cut out, the trim operation will remove the whole wall-group instead of cutting out what overlaps with the outerShell Group.
Hard to explain… I hope it’s obvious in the file.

The window- holes on the one side that i finished, i got by doing the trim on a surface without a pre-existing hole, and then pushing the holes after the trim.
But as my model already has the window-holes, i hope for an easyer way than deleting them all…
Not being able to use the window frames directly for the trim is complicated enough already.

This looks like a bug to me.

solid-tools-trim.skp (192.7 KB)

Have you tried the Solid Inspector extension? I found that entities I was trying to trim had “reversed faces”. I don’t know what this means or how it happened, but it generated some weird behavior. Solid Inspector repaired the reversed faces and made Solid Tools>Trim behave as expected.