I can replicate this with InDesign CC 2018.
But —on my machine— the issue is in no way limited (or caused) by KM Engine.
After a (short) test it seems the culprit is InDesign’s Copy PDF to Clipboard setting:
If this is selected then any paste attempt to any other app will result in a hang.
Steps to replicate:
Quit KM Engine
In InDesign set up a document with a text box as described here:
Create simple text box
Write any text in the box
Go to Object > Text Frame Options
Choose Auto-size - Width Only
Make sure Copy PDF to Clipboard is selected in InDesign’s prefs (see screenshot above).
Copy the text box in your document.
Now try to paste in any of these apps:
- Adobe Illustrator
- Or with Preview choose New from Clipboard (⌘N)
In every case I get the Beachball (hang) until I force-quit InDesign.
Even Apple’s Clipboard Viewer (part of Additional Tools for Xcode) hangs when trying to access the PDF clipboard content:
Also, if you invoke LaunchBar with your LaunchBar hotkey, it will hang immediately (it is also trying to read the clipboard, if its clipboard history is activated).
So, IMO, there is some incompatibility between InDesign’s PDF Clipboard and Apple’s clipboard API in general. (If the clipboard contains an auto-width box.)
The thing with KM Engine is that it is running constantly in the background, so it is trying to read the clipboard immediatly after copying, which makes you think it was the culprit. But obviously no app is capable to read that clipboard without hanging.
The easiest workaround: If you don’t need the PDF clipboard then disable the Copy PDF to Clipboard setting.