QDrag::exec() produces thousands of error message "combase.dll: Class not registered"

Calling QDrag::exec() gives hundreds and even thousands of the following message, even during a short drag & drop operation:

onecore\com\combase\dcomrem\resolver.cxx(2299)\combase.dll!00007FFDCC90206D: (caller: 00007FFDCC904F4E) ReturnHr(1) tid(3b3c) 80040154 Class not registered

QDrag object's modal loop gets so busy (probably waiting for the messages to be written out) that it becomes sluggish and appears hung.
Also, the drop event often gets lost when the messages are being written, causing the object to get stuck waiting for the dragging to end.
All the while, the same message continues to get written out.

Similar discussion is in https://forum.qt.io/topic/123927/qdrag-qdropevent-combase-error-class-not-registered/2

How to reproduce
Use https://doc.qt.io/qt-5/qtwidgets-itemviews-puzzle-example.html
and try dragging

Known issue

• Happen with touch panel device
• Both mouse dragging and tap dragging produce the same problem.