The UCS behavior in viewports depends on the UCSVP variable, and it needs to
be set in each viewport independently.
UCSVP = 1 - the viewport keeps its own UCS
UCSVP = 0 - the viewport uses the UCS current in other viewports
Also causing frequent confusion is the UCSORTHO variable:
UCSORTHO = 1 - UCS changes when restoring an ortho view direction
UCSORTHO = 0 - UCS stays the same when restoring an ortho view
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