We've made some progress with this file ... it appears that that groups are being created due to the presence of 3D HST selections and the way the saved data has been updated from one version of MC to another. More work continues to be done on it, but it looks like it should be under control for MC 2023. Thanks for sending the file in. And ... it looks like crazy^millman is seeing lots of unexpected planes because the STEP importer will import them ... typically any plane whose name begins with "STEP_" probably came in that way. Likewise for planes with names that begin with "CATIA_" or "NX_".

if you can get away with it, rough it and leave a good amount on the side (what ever you can), then take a finish cut using a reverse helix endmill. This will push down on the plating so that it is supported by the substrate to minimize chipping and flaking. Just don't go as deep as the rough, I don't think you want to cut the floor with this tool. Once the wall is finished you can finish the floor with a traditional endmill and stay .0001-.0002 away from the wall. https://www.ultra-tool.com/image/pdf_files/UltraCatV2021.1web.pdf page 25 Series 329S Square End Four Flute • Left Hand Helix / RHC Downcut Milling

Unfortunately it's an issue of approved suppliers, and I also can't blame him for having concerns about the masking. The concerns seem pretty valid, but I'm not a plater, so there very well could be a way.

Get a new plater