I'm finding this happening as well: with a brand new document. If you alt-drag a single page it will duplicate. If you alt-drag two or more pages it moves them, even though it first shows the + symbol on the cursor to indicate you are duplicating them. This is on version 15.1.2.

We have released an update for InDesign CC2019 (v 14.0.1) which contains fixes for some key issues. If you are not already on 14.0.1 (build 209), then we recommend you to update to latest version.

If you still face this issue even after updating, please send the following information to santalwa@adobe.com :

Reproducible Steps –
• Error snapshot or video recording of the issue.
• Is the issue related to a specific document(s)/asset(s)? If yes, can you please share the document(s)/asset(s) with us? Please package the entire document(To package the document, Go to File -> Package)
• Does trashing InDesign Preferences and Cache help resolve the issue? Please take a backup of the same before trashing them.

Adobe InDesign team

Updating to InDesign 14.0 on Windows has made this occur suddenly as well. I can still drag and drop pages but I can not drag and drop DUPLICATE pages unless I want to dump them at the end of the document (which you almost never want to do).

To either duplicate or re-order pages CS5 will no longer allow me to drag the pages in the pages panel. I now have to use the right click option and choose from the menu to get it to do what I want. Is this a bug? I have re-started both InDesign and my computer to no avail.

This is happening for me too, all of a sudden.

InDesign CC 2018, Windows 10

I cannot drag and drop my pages in the Pages Panel.

Steps to reproduce: Try to drag and drop pages
Expected results: pages will drag
Actual Result: pages do not drag