I tried repeating the problem but am not getting any shifting.

One thing I notice is that you have some pretty large custom margins defined.  In your screenshot that shows the red template, I see a dot at the bottom middle that likely indicates your floating text.  If that's where you put your floating text in your layout, it might cause a problem because even though the dot is at the bottom middle, that would put the text outside your margins and that could cause problems with the floating text.

Also, floating text that is linked to a print is linked relative to the top left corner of the print.  Your template fills out the entire printable area given the margins but when you add your image, it is smaller (top to bottom) because of the aspect ratio.  That can also cause problems if you are using crop off because the top left corner of the print changes relative to your layout after the print is resized to fit in your template.

You might just try an experiment.  Instead of making those restrictive margins, change your print placement to Freehand and then just remove the margins and save a new layout that way.  The template should stay at the same size and location but the text will be allowed to move relative to the print without being restricted by the margins.

Regards,
Mike