Font size change after opening new window from split

Windows 10, operating two monitors: 4K and 2560x1600, with Qt Creator on the 4K monitor.  Split a window, choosing to open in a new window.  Drag the new window to the 2560x1600 monitor.  The font size to that document is reduced on the 4K monitor (from 10 to approx 7 - very small).  Other documents are not affected on the 4K monitor.  Closing the new window does not fix the issue.  Closing and opening the document in creator does not fix the font size. Restarting Creator does fix the font size issue.