Bizarre problem setting a custom property

[David Epstein]

From the message box, I type

	set the autoFitted of group “a” of stack “specs” to false

Works as expected.

But if I type

	set the frameOptions of group “a” of stack “specs” to false

Fails with this message:
	Message execution error:

	Error description: Chunk: error in object expression

	Hint: 

Various other property names also fail, but I can’t detect a pattern.
Any insights?

Many thanks,

David Epstein