I think, that's a known bug with GPU acceleration with InDesign CC 2017 on Mac OSX.
If you turn off GPU acceleration ( Rocket symbol ) it should work as expected.
Engineers are working to fix the bug.
Note: I cannot test this, because I am on an old MacBook Pro without much GPU memory.
If Uwe is right, you can test by choosing View > CPU Preview to test it. The command toggles between View > GPU Preview and View > CPU Preview.
Thank you so much, Uwe!
Thanks for the tip! I am so lost in this program some times