Hi developers,
this is a longstanding bug:

With facing pages documents on EVERY document page there is a zone where jumping of objects will happen.

I call this the jump zone. All objects on a page that will jump are clearly inside the page's area. The bug has nothing to do with rounding errors where object edges are at the edge of a page.

The objects should not move if pages are added or removed, if numbering of pages is changing. Nevertheless they do. Always. Unless, the zone has a width of zero.

Below all the details.

What is a jump zone?
If horizontal values for left and right margins differ, there is a BUG that in effect forms a zone on the page.
I call this zone JUMP ZONE because objects that touch the zone with their edges could jump horizontally.

When will objects jump?
1. When a left-hand page becomes a right-hand page OR a right-hand page becomes a left-hand page.

1. When a left-hand page becomes a right-hand page and later when a right-hand page becomes a left-hand page again.

This could happen within a single InDesign document open.

WARNING:
It could even happen to InDesign documents that are not visibly open.
That's with InDesign documents that are part of a InDesign book file.
The book file's feature with auto-numbering pages can do this even if no document is visibly open.
The damage is done if auto-numbering took place AND the book file is saved.

How large is the jump zone?
The height of the zone is the height of the page.
The width of the zone can be calculated:
inner margin MINUS outer margin

How large is the jump?
The width of the jump zone.

Where is the jump zone positioned?
Positive value: The zone is at the spine of the page.
Objects that touch the zone jump towards the spine.

Negative value: The zone is at the edge of a page away from the spine.
Objects that touch the zone jump away from spine.

What versions of InDesign are affected?
All versions CC up to InDesign 2020, Mac OS X and Windows.
InDesign CS6, Mac OS X and Windows.

Possibly also InDesign CS5 and CS5.5, Mac OS X and Windows.
I did not test this.

How can I avoid jump zones?
Make right and left margin values the same!

Are there workarounds if I cannot avoid jump zones?

1. Anchor objects
   that touch the jump zone to text frames that do not touch the jump zone.
   Nested objects will not jump if the parent objects are not touching the jump zone.




2. Group an object
   to another one that is touching the top or the bottom edge of the page.
   Tests are showing that objects will not jump if they touch the bottom OR the top of the page.
   ( OR both, bottom and top edges of the page .)

Other things to consider about moving objects?
The following is independently of jump zones:
Objects could move to other pages if their edges touch exactly the horizontal edges on pages in facing pages.
Depending on the version of InDesign this could also happen with objects touching the spine.
Reason: Rounding errors.

What can provoke all this?
1. Add or remove an odd number of pages
so that left-hand pages become right-hand pages and vice versa.

1. Renumber start pages of sections
   so that left-hand pages become right-hand pages and vice versa.

Note:
Every document has at least one section by default.
The start of that section is the first page in the document.

More details at Adobe InDesign Forum:
https://community.adobe.com/t5/indesign/bug-in-book-s-update-numbering-feature/m-p/10774458#M166408

InDesign 2020 documents attached here.
See screenshots and further comments at Adobe InDesign Forum:
https://community.adobe.com/t5/indesign/bug-in-book-s-update-numbering-feature/m-p/10774596#M166420

Download link to all test files on my Dropbox account:
https://www.dropbox.com/s/duov096cu2q481l/Jump-Zones-Explained-Facing-Pages-Documents.zip?dl=0

Regards,
Uwe Laubender

( ACP )

PS: Why does InDesign Uservoice not permit to attach files with suffix .indd ?
Message: "Invalid file type: .indd files not allowed."
Isn't that rather absurd?

When we create new documents with facing pages and Primary Text Frames on, new master pages are then created based on that original master page.

I would expect them to inherit the same threading and Primary Text Frame designation as the original, but they don't. Only the text frame on the right hand master page is designated as part of the primary text flow, and the frames are no longer threaded. Designers have to check every based-on master, re-designate the primary text flow, and re-thread the frames.

The steps to reproduce are:
1. Create a new document with Facing Pages and Primary Text Frames enabled. The A-Master spread has primary text frames on each page, threaded together.

1. Create a new master that is based on the A-Master. The new master spread only inherits the Primary Text Frame on the right hand page. The page on the left gets a basic text frame, and the frames are not threaded across the spread.

1. Adobe InDesign 15.0.1 x64 (Windows 10)


2. Facing pages document. I create a master page that includes two text frames per page--creating a two column spread on each page. I designate the leftmost frame as the primary text frame, and then manually link it to the frame just to its right. That frame is then linked to the leftmost frame on the right side page, and that one is linked to the frame furthest to the right. So the frames are linked, from left to right: frame 1 is primary, which is linked to frame 2, then to frame 3 (on the other page) and then to frame 4.

Using the pages panel, I manually insert four pages into my document, assigning the new master page to these pages. The first three text frames are threaded correctly, but then the threading goes completely haywire.

1. I would expect the new blank pages to replicate the text threading order that I created on my master page.




2. The text threading goes wacky. I have included an image to demonstrate.

This seems similar to the problem posted in this Bug report (34661228-based-on-master-pages-don-t-inherit-primary-text-f.html) however on the document pages my text frames ARE threaded, just not threaded in the same manner as they were on my master pages. Plus, I am using a much later version of InDesign than the one that fixed that particular problem.

I'm using a Mac and running Catalina, have ID 2020. Yesterday, an existing file of 33 pages stopped allowing me to save it. I had no idea it wasn't saving and lost hours worth of work by the time I realized what was happening. I tried starting a new document and pasting the text into it, but same problem. I started a new document again and it allowed me to save immediately, but the second I dropped in text (different text this time), I lost the ability to save the file. I can export to PDF or IDML, but cannot simply save the file.

Is a big problem: when moving pages from different Documents with the same options, master pages and Layouts the pages moved are shifted (to the left or to the right).
I've made an Example in the attached Files.
1.png shows the way I move the last two pages of the document to the other document (identical copy of the same file).
2.png shows the pages moved in the second document (they should be the same but the imported ones are shifted by a few millimeters).
For documents where you have to import hundreds of pages it is very frustrating to have to manually rearrange them all.