First, preview is known to be a bit buggy since CS5, so you should try without the preview step, and second, in the template it looks like the ruler zero point is set to the margin guides, and inthe merge document it's set to the page corner. You might want to set the template top the page corner as well, then reset the margins in the dialog to reflect that zero point, if necessary.
thank you for your answer.
I tried skipping the preview, it is shifted in the same way.
(The zero point is set to page corners in both documents - in template doc the margin guides are set to 0 so it maybe looks just different; anyway )
Here I startet a new document, zero set to page corners, skipped the preview - and the objects are again shiftet by 0,122 mm in the merged document
This looks like a rounding calculation error somewhere … why should 10mm suddenly become 9,878mm?
Is there a stroke weight listed for the frames, even though there is no stroke color?
Did you rebuild the template for the new test? Once damaged by a preview glitch, the templates never seem to work properly again.
i'm not shure how to translate "stroke weight", but the outline is set to 0pt (see screenshot above the "150%" in document title)
I restartet InDesign and built a new template from scratch to test this.