It appears that "Undo" (Ctrl + Z) does not work on 2.1.25. I use this often to back out of a material selection. ???
Bill G
Works just fine for me ... ?
I just tested a new, fresh, bip.
1) On first import, all is OK. Undo, etc. works fine.
2) Re-import same model, not merged, with "Retain Materials" checked, "Individual Parts" not checked. All OK.
3) Ditto, but with Retain and Individual both checked. Ctrl+Z not working, and materials will apply only to individual faces (surfaces) instead of the entire "part" as with 1 and 2 above.
So, now I re-import as a "raw" model only, and all is good to go. This issue does not seem to apply when you import two or more of the same model, merging them as a group.
Bill G