Do Userforms in a Shared Workbooks Close Differently than Unshared?

The users of a project I'm updating routinely have the main worksheet zoomed down to 75% in order to see all of the necessary columns on the screen at once. In order to avoid the "Not enough resources to display completely", I change the zoom to 100% while the userform is open, saving the previous zoom setting as a variable and restoring it once the userform is closed.

In Userform_Activate:

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In Userform_QueryClose

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This works fine until I share the workbook, at which time it stops resetting the zoom level when the form is closed. I've experimented with a button to change the zoom settings while the userform is open and that works fine, so I know it's possible to change the zoom programmatically within a shared workbook, so what would stop the last line of code from resetting the zoom when the form is closed in a shared workbook?

Two random bits of possibly useful information: ZoomValue is declared as a Public Integer (in a separate module) and I also tried moving the code from Userform_QueryClose to Userform_Deactivate but it made no difference.