I have part of a castle wall containing arrow loops, and wish to run a 1" x 1" chamfer around each profile. You will note that SketchUp fails to trim the supporting face consistently…
If the geometry is first moved to the origin, then the correct result is produced! (and the excess/unwanted chamfer side faces can then be deleted)
It therefore appears that SketchUp has an inherent deficiency processing tolerances for geometry far from the origin.
I would apologise for modelling my large local castle! - but it is no bigger than a small shopping centre and is thus not of unreasonable dimensions (I hope!).
(The original model origin/axes is central within the model)
I attach a copy of the geometry so that this serious issue can be reproduced and addressed, promptly (I hope!)…
V17 Follow Me defect.skp (22.6 KB)