Hmm, OK, if you can post or PM me the object in question, I can check why it is not working correctly and perhaps improve the script.
Brep is as Graham pointed out a “geek” term for a Rhino surface or polysurface. I used it simply because it’s shorter than printing out “surface or polysurface”…
The script is somewhat experimental, and maybe not all that reliable. What it tries to do is get all the individual faces of a surface or polysurface (brep), check to see which ones are planar, if it finds any that are, it gets all the edges and tries to create a new trimmed planar face using those edges. If that succeeds, the new face replaces the old one; if it doesn’t manage, the old one is kept. If a face is non planar, that is kept also. At the end, it tries to join everything back together into one object. If something goes wrong and it can’t do that, it simply discards all that, leaves the original and counts one object that “couldn’t be processed”. At the end the reporting tells you how many objects couldn’t be processed - that just means that they weren’t changed in any way.
So when you get the message that 1 or more Brep objects couldn’t be processed it’s simply because I put a fail-safe error trap in there, but we don’t have any real info as to why - in order to have that I have to step through the script with the object in question so see why/where it fails.