Thanks for posting on the forum, and sending the files privately.
Your document is set up with a baseline grid of 12pt.
A reduction to 6% will take that down to 0.72pt.
But InDesign only supports baseline grid division down to 1pt, that is, you cannot set the InDesign baseline grid to be less than 1pt.
To fix this: Before running the QuickResize, change the baseline grid interval, say to 24pt, or even 120pt (if you’re not actually using the baseline grid, it shouldn’t matter).
(To change the baseline grid settings: Preferences > Grids > Increment Every (at least, those are the terms in my English version of InDesign)).
Once the grid interval is increased in this way. QuickResize should run fine.
Does that work?