excel dynamic user form: sometimes form does not update recently changed object property

I have a vba user form where 95% of objects are defined dynamically. It's quite a big form
When adjusting layout, I change an object property in CODE  (eg ctl_checkBox.top = 34), unload the form, and re-initiate it.
But recently, I find that some properties like ctl.top and ctl.caption do not update their display according to the  NEW property value specified in the code (above).

At first I thought I was editing the property of wrong object (hence no change rendered to obj on screen).
However, I found that if, before making the DESIRED change in property, I first set the property to NULL (for .Caption) or a way-out different value for .Top (etc), THEN I got the desired change in property that was specified in the very next line of code.

It seems as though the Form ignored small changes (during editing), and needs a 'jolt' to wake up and take me seriously! Can you give me some top-ideas of possible causes, please. So I can probe about..

QUESTION:
Is there some probable rationale to this? Is this phenomenon 'telling me something' about an error in my approach to dynamic form creation? - I've created many before, but not quite so big.

Thanks, Kelvin