When the Page Tool is used to resize parent (master) pages, unwanted shifts of page items may occur. These can occur directly in the document or also after an IDML export. Whereby with the IDML export the order of the sample pages plays a role

Concrete example: When the right bottom corner of the Page Tool is selected and the page size is changed, a position mismatch occurs on the inherited master page.

It is expected that on master pages of the same size the position of objects and inherited object is the same.

This does not occur if the upper left corner of the Page tool is used when resizing.

You can see this also in the different matixes of the inner coordinate system of the master pages.

Resize master page in UI – top left corner selected:
app.activeDocument.masterSpreads[0].pages[0].resolve(AnchorPoint.TOPLEFTANCHOR,CoordinateSpaces.INNER_COORDINATES)[0];
› 0.0

Resize master page in UI – bottom right corner selected:
app.activeDocument.masterSpreads[0].pages[0].resolve(AnchorPoint.TOPLEFTANCHOR,CoordinateSpaces.INNER_COORDINATES)[0];
› 28.3464566929137.48.1889763764252

After the IDML export, guides are also partially displaced. See attached screenshots. Whereby here also the order of the sample pages in the page panel plays a role, thus:

Page Panel

A-Master Page
B-Master Page

or

B-Master Page
A-Master Page